I have a chance to buy a slant six from a 1969 Plymouth Valiant with 84.5K miles with an automatic trans (I have a 3spd manual I would adapt to it) for $250. I read that the 1969 engines have 145 hp/215 tq...quite a bit more than my '77...would the '69 engine benefit from the Super Six setup? What kind of gains would I be expecting? Would the intake/exhaust manifolds benefit from any porting/polishing? I'm just looking for a good streetable slant engine for my '77 truck instead of this 318 in my '72 parts truck that is tempting me to do a swap. I also was told that a pre-68 would need a pre-68 flywheel, but a post-68 will bolt right up to my 3-spd. Thanks for any and all info!

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-Brodie

1977 Dodge D100 stepside, slant six/3 on the tree
2002 Chrysler 300M Special (daily driver)

Actually, no. The horsepower rating system changed in 1972 from gross horsepower to brake horsepower. The pre-72 slant actually made a bit less power than the later slants, especially the Super Six slants, due to the smaller camshaft on all but the marine and export two barrel engines.
My advice is get the 69 engine, swap the Super Six system and the camshaft from your 77 motor to the 69, and take the time to pick the best head of the pair and get it machined to increase the dynamic compression ratio to around 8:1. Also properly degree the cam when you install it.

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Casually looking for a Clifford hyperpak intake for cheap.