This tells you what a 'project' this car represents--when I bought it, both
seats were completely unattached to the floor!

Talk about your 'free-floating anxiety'--good thing the seller drove it
here to drop it off, and not me!

So now I need to find out what size bolts to buy to put 'em back in
properly. Anybody know offhand? And do they simply bolt down to the
floorboard, or will I need to get underneath the car with lockwashers and
nuts as well?

I don't remember what size bolt and thread they are, but they simply bolt down to the floor. Clean the threads first and use a good threadlock to make sure they don't freeze to the floor making it tough to remove them later if necessary.

You can buy the proper bolts from any of the resto houses like Corvette Central, Eckler's, Corvette America, etc. That way you can avoid buying cheap, non-heat treated bolts from who knows where. A good auto supply house would have the proper bolts...I would avoid the bolts at WalMart, Home Depot or places like that. The bolts there are generally fine for general Harry Homeowner stuff, but you want to make sure you install good ones since it's your butt they're protecting!

They shoud be either 7/16 or 3/8 course thread size - 3/4" lenght will do it. As long as you buy grade 8, you can't go wrong. Use some lock washers and a small amount of anti-sieze compound on them when you bolt them in.  

Don't know if I would use thread lock on them. Seen plenty of them siezed without thread locker due to the exposure from the underside of the car...

Paul

LukesVette38864.7778703704

My bolts in my Pace Car were all rusty so I just bought a 8 bolt set from Corvette American for $6.  And they just screwed right into the floor

http://www.corvetteamerica.com/cf/displaylearnmore.cfm?learn moreid=1062&idlist=3629,959,5215,p_K1216,p_25837,2047,27 31,1062,p_25835,3541,785,4567,4254,2973,5138,4253,4875,2603, 1652,p_20993,1061,4557,4554,p_26022,4555,1062&searchdest =%2Fcf%2Flearnmorelist%2Ecfm%3Fsubcategoryid%3DX420&subc ategoryid=X420

cilrah38864.8519791667

Thanks to all for the info--now I know what to order, where to order it,
and how best to install them. I really appreciate the info.

I'm still planning on replacing the existing seats with the Pace Car/79-on
versions, because I want the extra bolstering; but before I do that, I'm
sure going to need the bolts to attach them! (Still hoping that the '78 seat
frame brackets I have are the same as the Pace Car/later years--it makes
sense that they would be, except perhaps for the power seats in the early
'80's models, but on the other hand...)