C3 Frame swap
Burning Brakes
Joined: Sep 2006
Posts: 1,071
Likes: 86
From: Rotonda FL
at the front between the 2 years.
I know that a 75 frame will fit under a 77 - I've done it - but I understand that this is as far back as interchangeability goes.
Drifting
Joined: Oct 2012
Posts: 1,524
Likes: 61
From: Medina Ohio
73 had a chrome rear bumper. 74 was the first year for the plastic rear bumper and had a unique one year only slide impact. 75 and on had the hydraulic impact absorbers.
I'm actually not going to say the 73 won't work, because all of the bodies will mount to all of the frames, but the 73 will be the most difficult swap, and you will not be able to use the 77's rear impact assembly. It will require custom fab work or go without any rear bumper impact structure.
The 74 will actually work, but you will also need the 74 impact bumper (I have one to sell). 75-77 will be a direct swap.
Gas tank mount will be the same until 78+.
I'm actually not going to say the 73 won't work, because all of the bodies will mount to all of the frames, but the 73 will be the most difficult swap, and you will not be able to use the 77's rear impact assembly. It will require custom fab work or go without any rear bumper impact structure.
The 74 will actually work, but you will also need the 74 impact bumper (I have one to sell). 75-77 will be a direct swap.
Gas tank mount will be the same until 78+.
Race Director
Joined: Oct 2000
Posts: 12,687
Likes: 3,139
From: Shamong, NJ
The 73 and 77 frames are basically the same. The main difference is the rear cross member and rear frame rails. We're talking about maybe the last 8-10 inches of the frame. If the rear of your 77 frame is good, it would be easy to have it welded to the 73 frame.
The front frame horns should be the same on both frames, though you may need to add a couple new holes. Both frames are the same at the front, I just can't recall right now if all of the holes are in the same place.
The bigger question, involves which transmission you have. Corvettes with automatics, came with a removable trans crossmember, while 4 speed cars had a welded one. If your car is an automatic, you'll want to make sure you buy another automatic frame, or you'll need to swap the crossmember and brackets from your frame, into the 73 frame. If your car is a 4 speed, then either a 4 speed or automatic frame, will work just fine.
The removable crossmember is a plus, if you have a 4 speed, but you do not want an automatic, with a welded crossmember.
The front frame horns should be the same on both frames, though you may need to add a couple new holes. Both frames are the same at the front, I just can't recall right now if all of the holes are in the same place.
The bigger question, involves which transmission you have. Corvettes with automatics, came with a removable trans crossmember, while 4 speed cars had a welded one. If your car is an automatic, you'll want to make sure you buy another automatic frame, or you'll need to swap the crossmember and brackets from your frame, into the 73 frame. If your car is a 4 speed, then either a 4 speed or automatic frame, will work just fine.
The removable crossmember is a plus, if you have a 4 speed, but you do not want an automatic, with a welded crossmember.
Safety Car
Joined: Sep 2003
Posts: 4,206
Likes: 8
From: Belmar NJ
The basics (wheel, engine, trans and rear locations) are virtually unchanged from 1963-82. The big differences are bumper mounts, gas tank mounts and body mounts. How big a project it is depends on your abilities. This is a good reference http://www.71corvette.com/frames.html
