Advance Adapter kit installation cost.

[grago1978]

I'm still in the planning stages of this and pricing it out. I'm going with the old reliable 302 and AOD combo. My question is what is the average cost to have the tail shaft replaced on the AOD with the one from the AA kit?
What charges should be expected from a competent shop?
P/N 50-8404 - AOD (1988 & up) to Borg Warner 1350 T/C. Adapter length of 9" O.A.L. 29.500".