flathead cam in a 195.6 OHV?

Couldn't you have the a flathead cam reground to reduce the lift?  

As far as I remember the cams interchange. Do remember that in 64 or 65 the bearing sizes changed, and if you have the late 196 with the oil to the head from the front cam bearing instead of oil gallery you will need to change the oiling line or mod the front bearing lobe to feed oil. The L-head didn't have provisions for the external oil line from the cam bearing, of course.

I wonder if AMC used the same cam blank and just ground it down for the OHV? I doubt that was done for production engines, would mean a lot more machining time and they made enough of the sixes to cast a different blank. L-head is 248 degrees duration, OHV 244. Look at the cam timing charts in the TSM -- profiles are close, but slightly different. Should be close enough to grind a little more lift for the OHV, but with the valve opening/closing events a bit off you might not get more duration. I had no problem getting 0.100" lift and 264 degrees from one. Doesn't help bottom end, but around 1800 or so it starts making power -- gives some passing/hill pulling/speed holding power from 40-45 mph and up (3.31 gears and 195/65R15 tires, M-35 auto trans).

Well, Lunati increased lift by 0.10" and duration by 20 degrees on my stock OHV cam. Base circle was just about against the main shaft area, so I don't think they could have got ANY more lift... maybe 0.01-2"... Not sure about duration. I don't think more lift would help much, but duration might. Biggest issue with that engine is the long stroke and small bore -- won't turn up much quicker no matter what you do to it, it's a tractor motor!  On the plus side torque comes up fast and curve is rather flat for a wide rpm range.  I know, preaching to the choir here...

The crank only has four bearings, but there is a lot of material there -- I don't think it would flex with 3-4 psi. The head sealing should be okay... the only problem area I ever noted with sealing is the right side, and that's not subject to compression. I wouldn't be scared to put 3-5 psi on a 196, but I wouldn't get all excited and go any more! Would probably go no more than 4 psi... and to keep heat down use a remote turbo. That head doesn't need a lot more heat!! maybe do it like most on the 232/258 and run the exhaust under the engine to the other side and mount turbo over there. Still under the hood, but shouldn't cook the head and carb so bad. On something like your roadster though, cut the rear floor pan out and make a space for a turbo there. The turbo housing effectively muffles the exhaust, so you could run without a muffler. I'd thought about that many times... but if I build another car it won't be 196 powered. REALLY considered running a 4-5 psi turbo on a flathead -- turbo bolted straight to the head with a suck through side draft carb would look wicked! Then I did the math. I'd have about 125-135 hp -- about the same as a 196 OHV... too much trouble just to get that!!

Stick your T-5 on the 4.0L. Hmm... the input shaft is too long though, since you have the V-6 model. A spacer plate could be made, but there is also a 3.35 first gear short shaft version, so you could change the input shaft. According to a chart on the Internet that was a service trans, not used in a stock installation, but you should be able to find a replacement input shaft. You don't use the stock heater anyway, so cutting out the center of the heater box to set the engine in (needed for the longer 258/4.0L!) shouldn't be a problem. See the 300 Ford posts in Frankenrambler for photos -- he needed to do the same.