[TheDark1]

When I built my 350 I ran a larger stock radiator out of another truck. Even though the air flow area was cut down because it was wider than the original, it still allowed more volume of coolant and had no problems. I just made some homemade brackets for it. I ran a cheap-o replacement clutch set-up from the local parts house in the stock 3-speed tranny. You'll lose traction way before you hurt that little 3-speed. I had 3.73 gears and it still howled down the hiway. The 400 should use everything that the I-6 uses except the exhaust. I'd put the 400 in and use exhaust manifolds with a real exhaust set up. They're cheap easy to find and won't give you a screaming headache on the highway. Start saving for an overdrive for next winter. Don't even bother with the M-22 unless you can drop the rear gears to a 3.50 ratio or lower. The Muncie doesn't have an overdrive so you'll be turning the same RPM's at 70 as the little 3-speed. It just splits the ratio's between 4 gears instead of 3, the final drive is still 1:1 in both. Find a cheap clutch set, a decent radiator and drop in the 400. You should be able to do that for way less that a grand. Oh yeah, on the 3-speed. My truck had 285 thousand miles on it when I got it from a field where it had sat for years. It had the old lube in it and I used to do clutch drops at 5000 rpm's and wait for it to shatter. Never happened.