i didn't intend to disparage the S6 in any way. It is a great engine in its own right, being the baseline engine for many of Chrysler's cars over its very long production run. Anvils can only look on with envy regarding its reliability.
The issue, in my mind, with the S6 is not the S6 itself, but its misapplication in the J bodies. Put simply, the J body weight is just too high for the S6. The 318-2BBL is barely adequate (130 HP or so), the 318-4BBL is getting closer to the ideal. Reality is, the J bodies would have had the 318-2BBL as standard if Chrysler was not as overly concerned with CAFE in the early 1980s. Ideally, the engine line up would have been 318-2BBL base, with the 318-4BBL and 360-4BBL as options. However, it was not to be, and you can't change history.
In today's world, with the freedom to do anything you want, I think the ideal combination would be a 318/360 built up the way wrote about above. Should have a pretty strong running engine, I would think somewhere in the 250-300 HP range, with good torque and drive-ability, on regular gas. Teamed with an A518 4 speed overdrive transmission and a rear end geared at 3.55 (in a 66-70 B Body differential) , it should be a great all around street car. The other approach, is to get a carbureted Gen III Hemi and its 545RFE 5/6 speed automatic transmission, a much more involved swap (with all the computer/ignition related issues), but doable. In either case, they will both make for a great looking, great perfroming all around car that can be daily driven without a problem or hassle.
Kostas