I'm new here but I just bought a 91 Power Ram 50 4x4 3.0 V6 with a automatic 4 speed. The engine runs pretty rough and the overdrive doesn't work. I am looking to either rebuild or replace the engine here shortly but I don't know what matches up to the transmission for a replacement engine. What do you all suggest for a rebuild kit or a engine swap? I want to keep the transmission because I will need the 4x4 in the winter. Also how can I fix the overdrive?

Thanks in advance for any input.