For accuracy, the '67/'70 Chevy would be okay. The Model King 1970 Wildcat would be a little easier for you to work with, though, as it's closer in size to the Olds for length and wheelbase.
The Wildcat had a 123.2" wheelbase per the 1969 specs, which are identical to the 1970. The Olds has a 124" wheelbase, so that's very, very close. Chevies had a 119" wheelbase in 1970, 121" for 1971-76.
I'd suggest finding a Wildcat and using the chassis from that. The Wildcat in and of itself is a nice kit, You might also like to see about having the chassis plate cast by someone and use the casting, or give it a shot yourself.
All you'll need is some Olds Engine Blue for the molded-in oil pan.
Charlie Larkin