Im from the 5.0 section and I swapped out my 2.3 for a 5.0. I hope my input helps a little here.
To do the V6 swap you would need a new k-member because they are different for the 4cyl and V6 but the 4cyl k-member will work for a 302, its weird and doesnt sound right but the 302 will sit right in with new motor mounts. If you are looking for more handling than power I would go with new springs, struts and go to a 5 lug sn95 brake conversion plus control arms. The sn95 axles I believe wont fit in a fox axle housing because they are longer but the driver side axles from the 88 ranger will fit so you would need 2 of them, heres a 5 lug conversion site
http://mjbobbitt.home.comcast.net/~m...tang/5lug.html
to do the 4.6 swap requires special motor mounts for your k-member (might need to upgrade to tubular k-member) and the computer plus all the wiring harnesses (PITA) but its been done.
the 5.8 swap requires a cowl hood because of the deck height of the 351W. heres a thread about 5.8 conversion
http://mustangforums.com/forum/351-m...onversion.html
All in all I would have to agree with sleeper inc, if you are trying to stay the cheapest route possible find a 2.3T engine with computer and wiring harness and try to find a 5spd with it if thats the way you want. It would be the easiest way to go IMO.
Like I said I hope this info works out. I have done some looking around and this is stuff I have read viz forums and such from people who were in the same situation as you. If any of this info is wrong I apologize and I hope someone will fix/correct my shortcomings.
Good luck with whichever way you choose to go.
~Chaoss~
*edit: If you are looking for quick easy mods right now, upgrade your throttle body and port your intake to match the TB. Port your heads exhaust ports to your exhaust manifold and intake ports to intake manifold. Get rid of the cat for a glasspack if you dont have emissions. New gears in the rear will help, alot. Get some spectre pieces from advanced or autozone and make a CAI.