auto to stick conversion

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I have a 1979 g20 chevy van with a 400 moter as well as a blown th350 I am wondring how hard it would be to replace that auto with a stick and if it isint to hard or if it is hard how do I go about doing so. I blew up the th350 by pulling a little too much weight. I thought about going to a th400 trans but it is hard to find a good one around for a good deal. with a manual tranny I dont have so nice to the vehicle. any information would be very helpful.