.... 230R65 X 15 on the front and a 255R65 X 15 on the back? .....
EDIT..... I use the 60 series on my 66's. 235 front, 255 rear.
Cooper Cobras are a quality tire which don't cost as much as the BFG's.
Keep an eye on DiscountTireDirect, both on their webpage and their eBay store. They often have some great promo deals or rebates.
Buick used a chev-rally type wheel on the 67's, with a Buick center hat. The hats are usually pricey if'n you can find them.