198

OK, that helps.

And I'm jealous, I had a 73 Duster /6 auto way back in the day. Wish I'd never let it go. Yes, upgrades motor-wise are similar between 198 and 225. The 198 will rev a little bit better/faster/higher, otherwise there's not a ton of difference.

Seriously, living in Canada, you will have to deal with cool to cold driving conditions. As if you didn't know. :rolleyes: Dutra Duals are a FAR BETTER option than headers. Headers on a slant are for all-out racing or a seriously pumped up street car. They are a waste of money and serve no purpose on something that's stock to moderately warmed up - and you will want the intake manifold heat system that's retained with the Dutra setup. Do the HEI conversion. The 2-bbl upgrade is a good thing, whether a super-six or aftermarket. Find a super-six distributor and do the recurve covered over at slantsix.org. So far, we're only talking about bolt-on stuff.

If you decide to get into the engine the head is the next candidate for improvement. It is the hindering factor in creating a good running slant. A nice street-level pocket porting job, larger valves, and getting it shaved to get your compression to about 8.2 (DYNAMIC not static) will make a huge difference. Depending on what you do, the next step is to get your cam reground to one of the moderate grinds by Oregon Can Grinding.

Upgrading the exhaust for better flow would be the last step. Happily, these improvements are all fairly reasonably priced.