Personally, I would look around for a GT or LX 5.0 before buying a car I knew I would want to drop a 5.0 in later.
If I were to buy that car I would make it go as fast as funds permitted with the 4 banger and use it as my daily driver and just take the 5.0 out on the weekends.
------------------
Too much to list. Best ET on the car so far with stock 2.73 gears - 13.73@102mph
Indiana Stangers Association
Buy your parts here
ICQ# 42269241