I just finished my project using a 67 bell and 66 block. All went well and it is awesome. After I finished I measured for the new driveshaft and needed a 50 1/2 U to U. I saw a lot of the parts suppliers had 51" driveshafts for around $400 for the conversion. While I was at Pick N Pull with my Uncle I started measuring every ford on the lot and what I found was mid 80's Thunderbird and cougars have a 50 3/8 U to U and whats more is they have AOD's so the yoke fit my T-5 and the small 3 1/4 U-joints bolted to my 8" rear. It was a direct fit and only $30. I also made my own Trans crossmember using my old one. Another bit of info I found is 4-door 90's explorers have a 51" Driveshaft and are aluminum. Only these have the larger 3 1/2" U-joint. They also have the correct front yoke but would need to have the 1310 to 1330 u-joint in the rear. To my surprise I had not found this info anywhere on the net. Hope this helps someone else save some money. I will post some pics this weekend.
Mike

 

aerostars have alum d/s too

 

Aerostars are 54 to 55"

 

yeah but the all wheel drive ones are bolt in for 5.0 mustangs from 79-93 since they are shorter