2.8L and 3.4L 60* V-6's were available in RWD. They were installed in Chevy S-10 trucks and Blazers, the GMC versions, as well as low and mid-range F-Bodies (Camaro and Firebird). GM has all kinds of racing parts for these including an aluminum block.

GM has shrunk the parts catalog on the 3.8L but the aftermarket has all kinds of parts.

As for the old 215 (3.5L) V-8, you'd have to find one and because they recent ones were in Range Rovers, they're more expensive. Plus there is vurtually no aftermarket support for parts. Newer EFI'd engines such as the 4.8L and 5.3L are smaller displacement, can be made to work with a carb, and will as little as the old 215. The 5.3L is aluminum blocked and use the same parts as the rest of the GM Gen III family of engines.

Newer transmissions will increase your mileage, but they are electronically controlled. All of the about engines will also work with your choice of manual transmission.