Have a 1975 Grandville convertible with rot in the frame. Will a hardtop frame interchange with a convertible frame?

hi Edj welcome 

have a chat to franks pontiac 

Vert frame is twice as strong as the hardtop.  Not a recommended swap.  Sorry, They (vert frames) are out there waiting to be found.

Edited December 20, 2024Dec 20 by JUSTA6

To explain Justa's answer a little more thoroughly, a convertible frame is specifically boxed or reinforced in key places due to the lack of structural support lost by the lack of the hardtop roof. The frame is beefed up to replace that lost structural support.

So you need a convertible frame to replace your rotted one since you have a convertible, or you have to know where to reinforce a hardtop frame by welding in boxing and reinforcing plates in key areas. Frankly it's cheaper and easier to find a used frame.

Therefore you need to find a '71-75 GM B-body convertible frame. That includes:

Pontiac Grandville/Bonneville/Catalina

Buick LeSabre/Centurion/Electra

Olds Delta 88

Chevy Caprice/Impala

Edited December 20, 2024Dec 20 by Frosty

Thanks this information is very educational for me , I'm going down the rabbit hole and restoring a 75 Grandville convertible so I'll be asking a lot of questions and thanks to everyone on this forum for their help.

Happy to help.

Keep us in the loop on your journey.