converting a 85 tub into a 73 full convertible

[CHAPS7931]

I am wondering how hard it would be to convert a 85 half convertible to a full converible like a 73 blazer. any help would be greatly appreciated. the reason i am asking is because i found a 85 tub for sale but I have a 74 2 wd frame that i want to replace that tub because its in bad shape.

[Zoomad75]

Take a look at this write up:

http://www.coloradok5.com/full-conve...nversion.shtml

That should get you most of the way there. Keep this in mind when chopping off the half cab of a later blazer, support. The factory full convertibles (73-75) had rocker boxes under the tub to make up for the support lost by not having a steel roof. You should add support back in if you plan on running without the top in the summer. Otherwise, the tub might sag with the roof off making the doors hard to open or close.

the 4x4 guys just end up with a cage to add the support back in, if yours is 2wd a full on roll cage might be out of place. You will have to do something to simulate what the stock rocker boxes do under the tub.

[Jonboy]

The floor is also a lot different. I think two of the middle frame mount locations are different. The rear floor was flat to right behind the seats up to 1977, 1978 and later had the rear floor dropped to right in front of the rear seat.

[Zoomad75]

Jonboy's right on the body mounts. Really you are looking a two distinct issues. One, convert the 85 to full convertible. Two, put the 85 tub on the 74 chassis. I would think that you should be able to cut the body mounts off of the 85 chassis and with those measurements in hand reweld them on the 74 chassis.

I wouldn't chop the top off until you get the 85 tub on the 74 chassis. That is unless you weld a bunch of bracing to the body to keep it from sagging when you lift it off of one to the other. By keeping the body un-cut on the swap you have less chances of it flexing or sagging on you making the body mounts harder to line up.

[Captkaos]

Another alternative is to put the 2wd stuff on the '85 chassis. If they aren't gone, you may want to see if you can integrate the rocker boxes onto the '85.

[CHAPS7931]

thank you all for the great info.

[Zoomad75]

Originally Posted by Captkaos

Another alternative is to put the 2wd stuff on the '85 chassis. If they aren't gone, you may want to see if you can integrate the rocker boxes onto the '85.

While that's simpler in the long run, using the 74 chassis might help him avoid the smog police in California. It all depends on if you use the vin from the 85 to register or if you can get away with using the 74 vin.

[Captkaos]

Originally Posted by Zoomad75

While that's simpler in the long run, using the 74 chassis might help him avoid the smog police in California.

Point taken, didn't notice the CA location. They would go by the VIN though wouldn't they. Proving the truck wasn't involved in a T-bone at the door pillar would be difficult for the DMV though....

[Baseball0684]

I have basically done what you are saying. I had a 73 2wd blazer which the body was rusted realy bad, so bought an 87 in decent shape and put that body on the 73 frame.

The main difference in the frames was because of the change in the floor. I had to cut a small notch for each frame rail on the part of the floor right before it raises up for the back and boxed that in. Also the crossmember which has the body mounts on it I had to take out because it was to high for the lower floor of the new body (i swapped the crossmember from the 87 in the place of the one on the 73 for the structural purpose, slight modifying and it fits) and you will need to take the ears off the newer frame to replace that middle body mount and bolt or weld them in place on the older frame. I personally didn't do this becase where I installed a 6 pt roll bar, the main steel channel welded on the frame right where the mount would be, and I used that as a body mount. The other difference I found was the holes for the body mounts on the newer frame were bigger, so in order to use the body mounts for the 87 I just had to enlarge the holes on the 73 frame.

Retrofitting the full top isn't to hard, I would do that last after you have the body mounted on the frame you are going to use being it will weaken the body. This was part of the reason why I put the 6 pt. roll bar in and welded it to the body also. Make sure you double check the gaps and the alignment with the top first before finishing the welding.

[Mr Pops]

I'm also planning on converting my 76 into a 73. I already have the top and the windshield frame cut off of a 73, and all the weatherstripping and plastic door plugs. I took a look at that link and it looks like they just chopped the windshield posts off and grafted the new one on. I'm going to try a different approach, not sure if its going to be more work or not.. I started drilling out all the spot welds on my donor windshield frame and am going to try to split the four layers of sheet metal and use the top and bottom layers only which will give me the top and bottom roof mounts. The idea is to keep the orig inner layers of my windshield frame intact, grind off a little led filling and tack on the 73 sheetmetal with no structural welding required. Also this wouldn't compromise the original exact shape of the windshield opening. I'm not a welder or a bodyman so any advise or comments would be appreciated!

[wildwilly4x4]

I'm in the process of doing the smae thing to my '80. I have modded the doors already for the full convertable, but I am still on the bench about the windshield mod. I have to replace my blazers frame before i can cut off my half cab (bad wheeling incident), but I dunno if i want to cut the pillars like they did on COK5 or try to separate the sheetmetal like the OP describes. Please keep me up to date on wht you end up doing.