personally , i dont go for bb cars. i'm into road racing and only do small blocks. however , there are people like a freind of mine that only have bb cars. as for worth , how much money you willing to pay for it > 10k , 50k , 250k ? its only worth what someone will fork over.
To answer your first question, yes. I would be all over it. I missed out on one a couple of years ago fairly local to me. It was an automatic but was still a genuine R code 68.5 coupe in nice condition with a drag racing pedigree. The guy wanted 25K and I didn't have it. I would've had to get a bank loan to swing it and while I was contemplating doing that a dealer snatched it up. It was on ebay within a few days with a buy it now of somewhere north of 50K iirc. I've owned two 68.5 R code fastbacks and would love to have another one in any body style.
68 1/2 R-code cars are exceedingly rare, and they only built 221 coupes (102 4-speeds). ANY collector would be "all over" a real one, but value all depends upon condition and completeness. You can't peg a value just on "hey, found an R-code coupe, what's it worth..."
Could be worth $50K, or it could be a $5,000 basket-case.