Allen, sounds like you have a 1 - 1.5 ton, and changing the engine won't gain you any road speed whatever, it's the rear end gearing that's limiting it, no matter how much horsepower you put on that low speed gearing it'll still be low speed
for starts on the 'freezing' problem, you should get someone knowledgeable to evaluate just what the problem is - like where did the puddle of oil come from and why? might not be a real problem at all
Bill
