[crazyjeenyus]

Here's a few things that I'm surprised no one has mentioned yet:

Look at installing a lump port kit in your head, those inline six heads were not designed well, and lump porting will vastly improve flow. Heck, even if you cut out the bolt bosses on the intake runners your flow numbers will increase substantially.
This will also allow you to more properly utilize a 4-barrel intake & carb and headers.

Another inexpensive upgrade that a lot of guys do is swap out your stock slugs with a set of aftermarket 307 flat top Pistons. They'll fit your block perfectly, and greatly decrease your rotating mass.

Now you can choose a cam, something in the 260-280 range would work well with the other upgrades. Always install new lifters with a new cam, and a set of roller-tipped rockers would be perfect.

This is about all you would want to do to a little 6 banger aside from adding a turbo or supercharger which I'm not really a fan of.

I'm actually in the process of building up a 292 for one of my projects ('50 Chevy Deluxe).

I've got some +.040 Silv-o-lite flat tops
And a comp 280h cam
Plan is to acquire a lump ported head and go from there.

Good luck with your 6. It's always nice to see one that's been beefed up, and they have a great sound.