It may be over kill, but I am sick and tired of not finding a 3 speed trans capable (at a reasonable price) of handling power/tq and a 4t60 is going to net me same reasoning/problems. Ideally if there were a 3T80 ever built that would bolt up (like the 4T80) and play right, I'd rather do that instead.
Are you using a 4T80 or 4T80E?
You are aware of the rear bolt that needs to be tapped and the ears need to be hacked up for this swap? Also, in order to retain A/C you will need to alter the mounting system a little using a H/L body style front mount and posibly still cutting the front frame crossmember.
I will probably look into this for the beretta still, if the cost stays affordable and I feel like making something of it I might just do it. Will not be the first or last experiment(s) that I have done and it might work too (like some have) .