8 3/4 ring gear change for optimum low end performance

2 years ago I swapped out my 727 for a 46RH transmission with a stock 5.9 magnum higher stall converter. I'm not sure what the exact stall is but the transmission came out of a 95 dakota with a 5.9 magnum. The converter is blue with a HS sticker on it and this is the only way I could know its high stall. It has a TF2 shift kit in it.
The engine is a 1998 5.9 mopar performance crate 300hp magnum with a 214/218* @ .50", .532/.539 lift cam, stock iron heads, eddy air gap and good breathing exhaust manifolds from treblig back when he was doing milled manifold work, dual 2 1/2" exhaust with an H pipe. Maybe around 350hp on the high rpm end. The rear end is an 8 3/4 truetrac geared with 3.55's. 27" tall tires. It runs great and I'm very happy with it's highway performance in overdrive and lock-up but I'm wondering how much I'm leaving on the table for low end torque. The rpm's at 65 in lock-up run at 1900. I'm thinking there's plenty of room for deeper gears but need some help finding what might be optimum for my application.
Any help is soo appreciated. I love it here and you guys are my go to when I can't find it in a search.