I did the T-5 swap in my 69 mustang and fortunately I found a tranny, bellhousing, and flywheel for 1000.00 I checked, and to buy the t-5 bell housing and 50oz. flywheel from ford was a little over 400.00 Then some conversion parts and cross memeber from
www.windsorfox.com were about 200.00. You will definitley need another flywheel and make sure it matches your harmonic balancer weight. I think the older mustangs had 28oz and the newer ones with t-5s have 50oz.(don't hold me to that though it's been a while since I did all that research) Good luck