your hp options are swapping the engine again to a 351w, then your possibilities are limitless, but really there is a website that ive heard of called fordsix.com check them out.
You can do a lot with the old inline 6 engines. Do a search for Clifford performance and they have some bolt on parts. It doesnt take a 351w to go fast.
Definitely go read up on www.fordsix.com. They have great forums there for people who want more out of their straight 6's.
Also, check out its parts site at www.classicinlines.com for a large variety of performance parts available. The biggest restriction to these engines though is the integral log head and manifold. The site owner of fordsix and classicinlines is nearly done casting an aluminum head from scratch that outflows everything out there with the exception of maybe the aussie crossflow. He'll also have manifolds to match it that are set up for fuel injection (injectors for each cylinder, not TBI)
Paired with other upgrades (cam, headers, ignition) it should be capable of nearly 300hp NA, and estimates with a turbo are over 400hp (Those are desktop dyno numbers though so YMMV).
It depends on your budget though as the head will run between $1000 to $1500 and the intakes will be about $250.
Once I finish rust repair on my 67 coupe, plans are to rebuild the i6 and add EFI, the new head, and a turbo. Should be a blast to drive.
1: if you havent already swap out the load-o-matic dist for a later model duraspark dist, and hook it to a chrysler ignition box and msd blaster 3 coil. i have done this already on my 66 falcon and it works great. engine lights off first time even on a cold morning(below 30 degrees) with NO choke and only two pumps of the throttle.
2: add a weber or autolite 2100 2bbl carb, or the offenhauser 3x1bbl conversion.
3: you can add a larger cam. classicinlines.com has a selection of clay smith ground cams that work real nice.
4: add a dual outlet header and dual exhaust. this is where you will pick a decent amount of power(after the cam swap) as the stock exhaust leaves much to be desired.
5: add a T5 and 3.55 gears.
these mods will really wake up your six, and you will likely surprise a few V8's in the process.
awesome you guys are really helpfull i do however have the offenhauser 3x1bbl intake so i need to pic up 2 more carbs and a link for all 3 . i will however check out those other sites thank you