Core support mount help?

[74CustomK20]

Hey everyone, I need some help. My 74 c30 has BAD mounts for the correct support. Sourced some new (to me) ones from a k20. Problem, the new to me ones are from a 81/87. I know the rubber bushings are different, but so are the holes to mount. Does anyone know if it's just the 81-87, or so I need to find some from a 73/80? I'm planning on a 4wd swap this winter, and want to use factory mounting if possible.

[sweetk30]

73-80 or 81-up is the split for the 2 styles .

and for the most part its the frame that makes the choice for what it needs .

i have used 81-up body's on 73-80 frames with 73-80 mounts no problem .

[74CustomK20]

Hmm, interesting. Measuring the holes is what messes me up. The 74 top holes are 1-1/2" apart, and bottoms are 2" center to center. The 81-87 I have are 1-3/4 top and bottom, which is what's confusing me.

[sweetk30]

unless you post a pic i got no clue what your telling me at this point .

i know the frame bracket hole is way smaller on 73-80 over the 81-up so the 81-up bushings wont drop in them unless you open them up .

[USSkoval]

Originally Posted by 74CustomK20

Hmm, interesting. Measuring the holes is what messes me up. The 74 top holes are 1-1/2" apart, and bottoms are 2" center to center. The 81-87 I have are 1-3/4 top and bottom, which is what's confusing me.

The earlier C30's used a different mounting hole pattern for the core support mounts.

[74CustomK20]

That's what I mean, the 4 bolting points on the side to actually mount it on the frame. I tried to upload pics, says I need a security token? Never needed that before.. but that's my problem USSkoval. If I found some from a 73-80 frame, should be good to go right?

[rpmerf]

https://www.rockauto.com/en/catalog/...body+mount,673

ENERGY SUSPENSION 34103G

It's the full set - radiator, cab front and rear. 73-80. $70.

[74CustomK20]

Originally Posted by rpmerf

https://www.rockauto.com/en/catalog/...body+mount,673

ENERGY SUSPENSION 34103G

It's the full set - radiator, cab front and rear. 73-80. $70.

Correct, but I need the frame mount, that rivets on. I am curious if 1/2 and 3/4 is the same as my 1 ton, after finding out 81-87 are different.

[74CustomK20]

Small update, I found a set of 73-80 1/2 ton 2wd mounts, and they look identical to mine, as in staggered mounting holes. Now if I can confirm that 4wd will be the same (and I don't see why they wouldn't be) I'll be good.

Link to the mounts
https://www.ebay.com/i/273574582933?...d6428fffd53fb5

[rpmerf]

Rock Auto shows that mount kit as fitting C20, C30, K10, K20, and K30 73-80. I know C10s have different rear cab mounts, but I don't know if the core support ones are the same.

[74CustomK20]

Originally Posted by rpmerf

Rock Auto shows that mount kit as fitting C20, C30, K10, K20, and K30 73-80. I know C10s have different rear cab mounts, but I don't know if the core support ones are the same.

Correct, but ny pieces in question are the mount that attaches to the frame, and their mounting spread pattern. I've been thinking of just ordering those 2wd ones...

[sweetk30]

your first round of info didnt specificly say frame mounts that riviot to the frame the body mount sits on .

so 2wd and 4wd have different front mounts on the frame . the lower half has more so the 4wd leaf spring hanger will attach to it .

now if you want to use 4wd on 2wd i dont see why you cant . you will just have some extra stuff is all . but i can not confirm this 100% .

[USSkoval]

Originally Posted by 74CustomK20

That's what I mean, the 4 bolting points on the side to actually mount it on the frame. I tried to upload pics, says I need a security token? Never needed that before.. but that's my problem USSkoval. If I found some from a 73-80 frame, should be good to go right?

For some reason it says I need a security token too. I'm not sure what that means at all.

I know of a guy on another forum doing a 4wd swap on a '74 crew cab. The '73-'80 B52 mounts he bought to use needed modifications to fit the shape and hole locations on the frame. Which means the stock brackets will not directly bolt up either.

I've got a '78 2wd Burb and a couple 70's K trucks too, I'll do some measuring tomorrow. I'm going to be doing a 4x4 swap on the Burb, so this is info I need to figure out anyway.

[74CustomK20]

Thanks Andy, I've debated on keeping it 2wd but a 4x4 is more practical in my use, plus a lot more desirable in southern Indiana. I know the 2wd brackets are 1-1/2" apart on top and 2" apart on bottom, but I can't see any reason why the 4x4 mounts will be different, know what I mean?

[USSkoval]

My '78 C30 Burb has the staggered mounting pattern for the core support mounts. Roughly 1.5 across the top, and 2.0 across the bottom.

My '79 K30 has the even spaced mounting pattern for the mounts. Roughly 2.0 across the top and bottom. In daylight, I can confirm it's the same as my '77 K5, but I'm fairly possitive it's the same.

[74CustomK20]

So they are different from. 2wd to 4wd... Figures.

[USSkoval]

It's nothing a little bit of drilling can't take care of.

[74CustomK20]

True, but which mounts do you go off of? Droll the frame to theounts specs or vice-versa? Guess of you mount the core support up and see where it lands n go from there...

[USSkoval]

My plan is to mount them up so that they line up to the core support. That should put the two different mounting patterns at a shared center. Then drill/slot to get 4 grade-8 bolts in there with hardended washers and locknuts. Any slop in the holes shouldn't matter because the spring hangers and little support brackets will will have their own set of fresh drilled holes in the frame.