After some thought, here's my take - the '89-'91 3.0L SOHC makes peak torque at 2500rpm and stall speed on the '89 OE non-lockup converter is 2100-2400rpm (mine tested at 2200). I would assume that the '91 lockup unit is the same stall speed since there's no engine change. It makes sense to me to keep the stall speed ~500rpm lower than peak torque so developed power isn't wasted and acceleration decreased by allowing the engine to over-rev the power curve. The 3.0L is a grunter and I'm afraid that if I get up around 2500 stall speed it might be a bit high and produce a negative performance effect. A lower stall speed should also allow the transmission to run cooler and increase fuel economy compared to a higher stall speed.
OTOH, if I put any boost on it the torque peak might go up slightly and a higher stall speed could maybe be effectively used under boost without a major impact on non-boost starts. More likely, boost would not result in a change in the torque peak location - just generate more torque.
It looks like a toss-up depending on what I do with the engine - but for now it would appear that the best choice would be the lower stall speed since the truck doesn't lack in initial acceleration and pulls well at lower rpms as long as speed is below 55mph and in any other gear but O/D.
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