mercury cougar motor swap question

I am working with a friend on a 1988 merc cougar with a 3,8l v6. We would like to do a 5.0 h.o swap. We are wondering if the transmission will bolt to the 5.0 etc, or what all will be involved in the swap. Some good detailed info would be very helpful. along with possibly ideas on other motors, and what would be involved etc. We have tossed the idea around of doing an old school 302 build as well. All input greatly apreciated.