I am new at this reso game so I don't have a lot of experience, I just got the quarters for my 68 coupe from OER, got them at Classic. They are very nice, the metal is good quality, it seems to be the same gage. The body guy that's working on the car said they were very good. I know everyone has there own experience with different companies, my body guy said that he has used Goodmark before and that they were usable but that it took a lot of work to get them to fit right. So thats all I know about that. I have a few pictures of the quarters I bought on the link on my info.
I bought goodmark rear quarters (from Matt's Bowties) and I felt that the drivers side was 95% correct. The passenger side was 99%.
The rear edge of the driver's quarter was the worst fit, and the jamb vent cutout seemed to be tipped 20 degrees. (enough to make us re-work it)
But as far as fenders go, I thought I'd be smart and buy NOS GM fenders. When I bought them a couple of years ago, GM still had about a dozen of each side left. I don't think there are any remaining today. Anyhow, after purchasing, there was a whole lot of threads on this site about them being "GM approved" repops, not true "OLD STOCK". (please don't start the barcodes verses non-barcode posts).
Long story short, they looked beautiful, but when we placed them on the car, they both still took a whole lot of bodywork to get them to align and match. A good friend of mine bought goodmark fenders (from Matt's Bowties) and the fit was about the same as my supposed GM ones (for less than half the price).
So I would reccomend Goodmark for front and rear sheetmetal.
I used to be indecisive. Now I'm not sure. I feel like I am diagonally parked in a parallel universe. 1968 400 convertible (Scarlet) 1976 T/A - 455 LE (No Burt) 1976 T/A New baby, starting full restoration. 1968 350 - 4 speed 'vert - 400 clone (the Beast!) 1968 350 convertible - Wife's car now- 400 clone (Aleutian Blue) (Blue Angel) 2008 Durango - DD 2008 GXP - New one from NH is AWESOME! 2017 Durango Citadel - Modern is nice! HEMI is amazing! 1998 Silverado Z71 - Father-daughter project 1968 400 coupe - R/A clone (Blue Pearl) (sold) 1967 326 convertible - Sold 1980 T/A SE Bandit - Sold