Will this DE-value my Longhorn????

[jku72]

I bet not only would it not lower the value, it would likely increase the value, but only if it's done right. Use all new parts.
I see no problem at all with the 200 r4 trans, in my mind it's worth more with the OD trans because it takes a dent out of the 4:10 rear gears. Gas is $3 a gallon. I've been thinking of a similar trans change in my longhorn.
I really don't care for power windows though, but I am in a minority opinion there.