Sid, I have thought of it---I have 2--
but I haven't found Trans companies who would speculate how well the OD would hold up with 1000-1500 HP ---also the 2.48 low would could be a bit much but it is something to REALLY consider---then with maybe a lower rear ratio
I think the 4L80E is a great transmission and have one built by the same guy that has been building your transmissions and it would be fine at B'ville to those HP levels in 1-3 but also question the OD handling it.
Not sure the others know what you are trying to do or not. With the powerglide you would like to go 1st, 1st overdrive with the Gear Vendors, then to direct and not overdrive and then overdrive.
Not sure if your PG has the 1.76 or 1.82 1st but if you could split the gears like you want to then I think you would end up with better ratios than the 4L80E that has 2.48 (1st), 1.48 (2nd), 1.00 (direct), 0.75 (OD).
With the 1.76 PG you would have 1.76 (1st), 1.37 (1st - OD), 1.00 (direct), .78 (OD)
With the 1.82 PG you would have 1.82 (1st), 1.42 (1st - OD), 1.00 (direct), .78 (OD)
I know that splitting the shifts is not easy from the driver's standpoint and takes time but might not big a deal at B'ville with the longer track vs. El Mirage where you are done so quickly.
Another option but probably not enough space in the car would be the 4L80E with the GV OD behind it.
Probably forget 1st (except maybe El Mirage) but 1st OD might be good at 1.93. Don't use the 4L80E's maybe weak .75 OD but use the GV .78 OD.
Ratios would be 2.48 (1st), 1.93 (1st - OD), 1.48 (2nd), 1.15 (2nd - OD), 1.00 (direct), .78 (GV -OD) Might not use all of those and maybe with the right rearend at El Mirage use 1st to direct and take advantage of the .15 drop between 2nd-OD and direct.
Lots of options, give us something to talk about when I see you next week,
Sumner