I am working on a Buyers Guide for Chevy Squarebody trucks and would love to hear some inspiration from others out there that own/have owned one!
My family has dabbled with Squarebodies for years. Some lessons:
-the first years didn't have drip rails --which some prefer, but provide a great opportunity for a body shop to mess up when they install the drip rail wrong after the cab is all painted. Next time... test fit the drip rail (and hole drilling) while in primer.
-not all firewalls are the same (at the very least A/C vs nonA/C in the early years). This bit us hard on a body swap when a usually reputable seller shipped us a southern cab that was wrong for our application and wouldn't make good.
-grill and trim differences in many of the years, especially the 70s. Do your research if restoring. LMC truck and Squarebody Syndicate, 73-87chevtrucks.com have parts/insight/inspiration ---you want to look up goofy things like front frame horn differences too.
-it is very easy to bend some of the hoods in half, especially with seizing hinges. Both hinge extenders and reinforced hoods have been on the market
-they changed the gas door from round to square, and the tailgate 3 (?) times so again preference vs. restored accuracy
-in our rust belt area... a perfectly good box can be completely gone under the stick-on trim that came around in the 80s
-there are subtle annoying changes in some of the dash board bezels. You are not crazy --some don't quite fit each other.
-door panels change a few times (and vent windows iirc) but you can swap entire door assemblies no problem. Some of the door panels can cover the older doors but you may have regulator and such mismatch.
-(some of) the big trucks use the same cab but have a flat floor. If you are cutting the floor out anyway... just watch out for big cabs with different cowls due to having different front ends. At the very least, big cabs have interior parts and doors that swap over (except the variation with notched doors --which was all the big trucks in previous gen)
-some stuff was changed into the 80s. Depending on who you ask "made lighter/better" or "made cheaper" can be the opinion. These attitudes mostly seem to apply to the 4x4 frames and running gear.
@Pepperallswas pretty thorough.
I will echo his comments on the hood braces on the earlier trucks. They are a must on those trucks, no exceptions.
I have noticed the most common rust spots being cab corners and rocker panels.
Dash pads almost always crack, finding intact ones is an occasion worth celebrating.
I have seen only a couple trucks optioned this way, but a factory tach could be ordered, they took the place of the giant fuel gauge.
My family has had many 454 trucks over the year and here is one interesting thing we've found. There are two different intake port sizes on the trucks, "oval port" and "peanut port". We have found the larger oval port heads on trucks through 1978. These larger port heads respond very well to even mild upgrades. Peanut port heads, we have found on 1978 and newer 454 equipped trucks. In anything other than a stock restoration, the peanut port heads have little to no performance value and are worth their weight in scrap and can't be given away. We've tried.
@Pepperalls @Greg_I thank you both for your insights. I am going to try to add these into the guide, mostly because my experience with them is limited. For reference, here's what I did for the 65-73 Mustang, of which there is a lot more documented information about: https://www.hagerty.com/media/buying-and-selling/your-handy-1965-73-ford-mustang-buyers-guide/ .
This 1986 Chevy C10 has been in our care for a few years, now. However, it's not going to remain stock and is currently slammed. (Vehicles never stay stock at my house).
The main issue/repair was rust in the cab corners. Moisture was stuck in the inner walls of the corner due to a drain hole being clogged.