Change from 4-speed to 3w/OD

I have 2 iron 833od, one in my 64 dart, I have 355 limit slip 83/4 stock wheels and a built 340 pushing it .
1st gear is a waste and only gets me to 30ish, if I try to power shift it into second the wheels break loose, but it is really hard to shift it into second. Forget about down shifting into 1st it just wont do it. revs are pretty low in overdrive but it lugs if I am going under 40.

Bottom line is it is OK for just cruising around but if you want to have more fun consider something else.
I have purchased a regular 833 and am going to swap it out as soon as I get all of the parts I need, and time to do it.