The stock 904 lock up will drop engine rpm about 200 rpm but the gear set is a 2:45 low gear like a normal early 904. The A500 uses a low gear set with a 2:74 low gear.
I built my A998 lock up with wide ratio gear set to get best of both , low end torque with 2: 94 rear gears ( pulls out like 3:23) and has lock up in high gear at 1to 1 ratio.
Lon