Average decent price: $1000
Some wreckers may do the conversion for similar money to that, and take your old tranny as a trade-in. This is currently what I am thinking of doing.
Please also note that there are countless threads on this topic around, especially under the 'Modifications' forum.
Jack Travis, E-Series Acting President
1989 Ford Fairmont Ghia turbo/GL replica (underway)
1994 Eunos 800M
1990 Ford Laser S