Ok, one I6 to a next, I think I can help a bit. The inline 6 is a torque motor in stock form. Due to the long and heavy crank, this motor will respond better to low-end load better than a comparable V6 or V8. However, with your flathead design, the options begin to dwindle. Air flow is an issue. Clean out your intake runners, replace/rebuild your carb and inspect your block for any stoppage points. If your going to upgrade your ignition, Go 12 volt(If you havent already) and save yourself a headache. Turbo with an I6 is an appealing concept. Due to all of the exhaust gases going through one manifold, theoretically you could get a good push through a turbo. It would take some custom piping, but it could be done. A Very viable option is shaving the heads. As with any motor, this will raise compression and create a few more ponies. However, i would reccomend aquiring a replacement head prior to this should anything go wrong. a 4.0 or 4.2L swap is an option(4.0 is EFI, 4.2 is Carb), but it wouldnt retain the origional look. It may be possible to use a distributor from one of these engines, and I would lean towards the 4.2 or its Earlier AMC designs. Remember, AMC bought willys in the 60s/70s, so there are bound to be some carried parts. As for camshafts, Anyone who makes performance parts for jeeps should be able to make your camshaft. Just relay the measurements of your current camshaft(Length, thickness, lobe seperation) and they should be able to make a custom piece for your block. Good luck with your motor. I6s run forever for a reason