6 cylinder gurus... need opinion

'76 disc brakes are nice.

If you have your heart set on an earlier motor, try a www.car-part.com search. Remember to search something pre-'68 as well as something post-'68 to get all the applicable hits.

First year for Super Six was '77 in North America. Only difference is intake manifold, carburetor, choke thermostat, air cleaner, and throttle/kickdown details, which means you can "Super Six" any slant-6.

Forged crank up to midyear '76, cast crank after that. Unless you are going X-Treem racing, there's nothing the matter with a cast-crank engine. If your '65 is an automatic, you'll need to remember to install the bushing that adapts the '68-up large crank counterbore to the '67-down small torque converter nose.

Wanna beef up the slant-6? You'll hear the name "Clifford" come up, but be very careful before you decide to spend any money with Clifford. They have a long and ugly reputation for being a bunch of clowns; see for example here, here, here, here, and here. Much of what they sell is inaccurately described, and a lot of it is not even slightly cost-effective. The good news is that you don't need to go to Clifford to get hot rod parts for slant-6s; there are lots of other, better options. See for example Dutra Duals and header options discussed in this thread and this one, Erson custom cams, HEI ignition upgrade, Mike Jeffreys windage trays, Hurricane intakes, other exotic intakes. Hi-perf engine buildup here, high-perf parts and build info here.