After searching the planet for a primer for the bottom side of my 67 GT500, I found something that works for me and may of use to someone else. As you can see in photo 1 my old primer wasn't in bade shape after it was cleaned off. I resprayed with 11 spray cans. Photo 2. The color was extremely close and so is the sheen. Not gloss or flat. It is an acrylic enamel from Krylon's Industrial line. Took a couple days to dry and appears fairly tough. Fairly hard to find as well. I ordered a case: http://www.globalindustrial.com/gcs/prod/30137714/i/productInfo.web?utm_source=shopping&utm_medium=cpc&utm_campaign=AerosolPaint-shop&infoParam.campaignId=WP
Looks pretty "flat" IMHO if the pictures posted truly show what the finished surface looks in person. Originally the surface was smooth and slightly shinny since it was not a simple primer but an epoxy primer sealer. Just one opinion of course Don't forget to remove the exhaust mounting stud places and rear seat belt bolts and clean them off - since they would not have been installed at the point of floor color application
Since you are concerned with details i thought you would want to know also dont forget to use the black sealer around the outer seat belt anchor like you did with the inner seat belt anchors. The base of the rear leaf anti wind up snubber is cast iron finish not black . The best of luck with your restoration. Bob
Thanks for the reminders, haven't started to detail yet, wanted to see if the paint was going to work. It may seem a little flatter in a photo, but it is definitely a nice semi gloss finish. Actually says gloss on the can for some reason. This would be a flat finish: Eastwood paints have worked out very well also. Detail Gray and Spray Gray are great colors.