Gentleman I drive a 41 plymouth 2 dr sedan it has a 250 chevy six with a 700 R 4 tied to a 9" ford with 3.50 gears. The engine has a open chamber head with 1.94/1.60 stanless pro flow valves and the head bolt boss is shaved to a point and and thined plus ports arre polished with some bowl work. The cam is a complete kit from Comp cams every thing from the gear on the crank to the rocker arm nuts, 260 H grind. The block is bored .030 over and decked around .018 (trusting memory but I'm close) 307 pistons ARP rod bolts in rebuilt stock rods. The cyl head was cut about .020 to clean it up. I run a complete MSD ign (distributor,coil and 6A box). I run a Q-jet setup for a V6 GM engine (85 Astro). Exhaust is a 292 manifold with the three bolt 2 1/2" out back to muffler which has two 2 1/4" outlets then piped out rear to edge of back bumper.
Everyone talks about what works well on the street and what doesn't. I tow my T roadster behind my Plymouth with no problems, we tow at legal highway speeds. If you doubt this talk to people who was at Iowa in 2008, or in North Carolina at the NTBA nationals in 2009. I live in Ohio. I think this gives an example of what can be done with an inline six. By the way the car is air conditioned and we use it all the time.
This is a no BS example of actual street use not what someone thinks. By the way it requires 89 octane fuel in flat country and likes 92 in the mountains.
Foot note don't bad mouth big block Ford sixes I put one in my roadster and it is amazing the performace to dollar ratio.
