[Joe7]

I just recently purchased a 1974 grandville convertible and I'm having a hard time finding parts.
I need quarters, trunk lid, dash, and driver door and quarter glass window.
What years and models body parts are interchangeable?

['ol Pinion head]

'74 GV convert 1/4's, like any full convert 1/4's are convert only. If you're only battling rust down low & around the wheel lip, splicing on a '74 GV 2 door hardtop 1/4 panel is an option. Over the years I've hauled in & parted quite a few '71-74 Pontiac Bonne's & GV's. On all 2 door models that had decent 1/4's, I removed the full 1/4's. On 4 door hardtop 1/4's, have cut off the 1/4 from in front of the wheel house, up, then back into the sail panel and then all the way back, including the trunk lip all the way back & down through the tail panel. With the removal of the headliner, seats, interior panels, sound insulation, harnesses, glass, gastank, rear bumper & bumper fillers, it's not a walk in the park to remove.

Dash pad, , best advice is to find someone well up North, who has hauled in what was often a garaged '71-76 B series Pontiac B series with a really soft uncracked dash pad assembly.
With so many '71-76 B series having been hauled in for their 455 or 400 engine cores, & just a few other pieces, nice dash cores are just gravy for the seller. In great shape, it would be best to reuse your guage assembly, ducting, AC control & dash bezels, etc. As you would prob have as much in careful bubble pack wrapping, double boxing & oversize shipping, if you are up N, it makes sense to search & retrieve this large part yourself.

Decklid, '74-76 Pontiac B series interchange for the bare decklid. Like any decklid, emblems & emblem holes often change year to year, reuse off your '74 GV emblems, or can double ck the interchange.

Door, as direct bolt on, fully loaded, the interchange is '74 GrandVille 2 door.
As a bare door, any '71-74 Pontiac B series 2door hardtop door shell can be used to load your original door pieces.

Glass.. I'll look up when back in the house.
To be quite honest, I've chunked every rear 1/4 glass & back glass I've ever pulled from this era Pontiac B series. Demand has been next to zero, & my main concern was removing them to expedite carefully cutting off the 1/4's or partial rear 1/4's.

['ol Pinion head]

Door glass & rear 1/4 glass fit all :
'71-75 GM B series convertible, that includes Cadillac Eldorados.
From a ton of boneyarding, & still getting out in some monster yards from time to time, it seems like the '71+ Olds Delta 88 Converts & Eldo Converts are what I consistently run across the most.

[newmexguy]

There are two dedicated Pontiac dismantlers and sellers in the southwest.
Meaning Franks, and Pontiac Heaven. They should have clean sheetmetal. Logistics is ridiculous now, so some type of Ushipper will need to be employed. Common carriers will be just too expensive now.
There's an individual in the Stroudsburg PA area, who parts out large GM bodied cars. Believe most are Oldsmobile, although he might have others. Believe his avatar is "bigdooly" or something close to that.
Have a personal friend in the Sherman TX area, he also buys and sells large seventies GM cars. He funnels what he finds and buys, to either WI or Atlanta GA.
He might have sheetmetal as well.
Personally never got into large cars too much, in terms of parts, as the market is small and sales few and far in between.