That's the advice I always give 'em, Roy--call 650 Central and talk to an honest man who knows what he's doing.
Justin, you don't need to worry about eyelet ID with Progressive (or most other aftermarket) shocks; eyelet diameter is universal, and the shocks are delivered with spacers that sleeve down the eyelets for particular applications. But eye-to-eye length is a critical matter. Lifting the rear will quicken steering, dropping the rear will result in slower handling.
As to selection, you might consider Progressive's Series 14 oil damped shocks. They stand up just fine in vintage racing, and they're far superior to original equipment. The Series 12 gassers are nice but they're a bit on the fat side, and you'll have to remove or modify the chain guard to fit them.