at the least you will need the frame mounts for a 302. also the maverick 302 engine mounts. a belly bar is reccommended. and the 302 needs a front sump oil pan and oil pump. might also need to change out the radiator to a v-8 one, but maybe not. transmission depends on what 6 you have. if it's a 250 yes, it'll work for a stock 302. 170 or 200 you'll have to change it out.
The radiator can be modified by a competent radiator shop. I have had one done before. It's probably best to buy a new one though to make sure you don't have any overheating problems but you may get lucky like I did (at least for about a year and then I had to buy one anyway). You'll also need to figure on an exhaust system which could run anywhere from $250-$500 depending on what you do...but well worth it.
if you hav a 250 the the rad will work with a v8, so will the trans as mentioned. 170's and 200's have smaller hose inlets on the rad and a smaller bell housing on the trans.
As mentioned earlier, the bellhousing will work if a 250 motor, and you need frame mounts and motor mounts... But any 6 cid rad will have to be changed... the hose inlets and outlets are on opposite ends and wont work with the early Windsor waterpump setup.
i know i am going straight to hell for this one.. But i was trying to find an aluminum radiator one time to go in my maverick.. wanna see the link? hahah i had a 2 core radiator, stock 170 car.. i put the 302 in it.. and the car continually ran into 240* area.. i went and got a 4 row EOM radiator from a 67 mustang, from www.radiators.com for 165 bucks...worked great.
hmmm.. are you running a later model 5.0 motor... because then they run the offset radiorator inlet and outlets on the rad because of the the different water pump. thats the issue i had with mine. I run a 289 so of course its an early windsor, with the early style waterpump. so i had to get all new radiator.
a 250 straight 6 rad will work. the 250 uses the same size hose inlets as a 302, the 170 and 200 hose inlets are a little smaller