i dont think the first gear of 3.67 is that bad...
but i also dont see why you would use the supra tranny that needs a lot of work running divorced and intermediate driveshafts and all of that, rather than a truck tranny that bolts a tcase to it...
L43 has a 3.67
L45, L50, L52, G52, G54, G58 have a 3.93
W56 a 3.95
R151F a 4.31
R150F a 3.83