haven't seen one but, having swapped a 57 onto an envoy, I have some experience with frame swaps. first do a track width coparison to see if the wheels from the newer frame will tuck into the fenders of the old cab without rubbing. especially if you want the truck to be lower than the old style, more like the "78 was. keeping in mind that the '78 likely had a smaller diameter set of tires on the front you may make it. will you be using duallies on the rear or a single wheel configuration? doing this to have an actual hauler or a lowered hotrod?
you will also need to figure out these items as well as the track width
-the obvious one here is the cab mounts. you will likely be best served to keep the cab/fenders/rad support etc from the old truck all bolted together and place it over the new frame so you can get an idea of how the ride height will be and what will need to be lopped off the newer chassis. start with the frame blocked and sitting level or at the rake angle (front to rear angle) that it would normally sit at with the rough weight of the cab sitting on it. then try to get the front wheels centred in the wheel openings as you and some friends lower the cab and clip down until it bottoms on the frame somewhere. try to find a frame drawing on the net or contact the gm heritage centre for a drawing with dimensions for the frame. they are great people to work with and get back to you pretty quick. the other option is to buy an assembly manual for the old truck which will probably have the drawing in it as well as how things go together and get adjusted to open/close properly (hood especially). you can try the link here to see what you find. look at several years of your body style because the notes are different each year ot seems
http://chevy.oldcarmanualproject.com...esto/index.htm
-will you use the stock cab mounts or the rubber mounts from the newer chassis
-I would suggest to take good measurements with pics of them so later you have a reference when the truck is dissassembled. snap pics of how everything comes apart because these projects have a way of spanning a few years to complete (trust me) and by that time you have forgotten which panel overlaps the other or what the pieces actually look like, as a quick example
-steering column from old to new. old truck was narrower here so it won't line up with the newer style box for width plus the newer chassis has a strg box mounted further forward so you would need to add some shaft length and some bearings inline to keep things moving properly without binding. you may also find the shaft may have exhaust manifold clearance issues with a v8
-firewall and floor may need to be modified to fit over engine/trans in newer chassis. I suggest to cross brace the cab with the doors on and fitting so they close well etc just so things stay in shape when the project is moving around and gets set down on the newer chassis. then mark each hinge well or drill 1/8 holes in the door/hinge bolt up area so the doors will go back in the same place. a pin can be placed into the drilled holes later for line up purposes. if you have an engine hoist you can fab up a quick cab lifter to lift the cab through the door openings so you can slowly lower the cab onto the chassis and hold it at any height while you block or fab mounts. that is how I managed to do my swap safely with only one guy in the shop-me-and no back injury or bandaids
-how to hang a set of pedals under the dash so they are secure. also power brake unit on firewall will likely require firewall support to handle the added stress of the push from pedal set
-if using a standard trans will need to come up with a set of pedals that will do the job plus assemble some sort of linkage. I would suggest a hydraulic clutch set up from a newer truck. there are aftermarket set ups with clutch slave cylinder in the bellhousing. not sure on price though
-track width and tire to body clearance with suspension fully bottomed and steering turned all the way, body mounts, firewall and floor clearance, steering column and linkage, pedals and brake unit (look at hydroboost to keep things smaller dimensionally), clutch and/or auto shift mechanism (could look at steering column from newer vehicle with column shift but cable operated linkage, like astro van? but they would have auto o/d trans so extra detents for extra gear), radiator and hoses, wiring, licensing and inspection, new vin to denote "assembled vehicle" and be the proper number of digits (Insurance Bureau of Canada) so you are covered if you have an accident. wouldn't want to find out too late that your insurance is going to "bow out" of coverage because the vehicle they insured has been modified but not disclosed to them. you would probably need some sort of roadworthy inspection as well. like anything else over 10 yrs old in Alberta.
I talked with the insurance Bureau of Canada representative responsible for this area and he said he would need to see a bill of sale for each vehicle, in your name, and also keep the vin tag from each vehicle (if the tag is removed from the cab for some reason, like sandblasting in my case) and he will take the old tags and issue a new vin for the unit and attach it to the cab. also it will be named "assembled vehicle) to denote that is was assembled from various units.
have fun but check into it first so you don't spend time and money for nothing.
pm me if you want to chat about other stuff on frame swaps