my stock 4l60e cant have long left... im debating on whether to replace it with another 4l60e with a good torque converter and do gears at the same time, or to swap a th350 in it with a good converter and keep my 2.93 gears .... i have 95 b body with an lt1 and stock cam and 27in tall tires
1. TH350 =
HUGE step backwards.....don't do it! it's not stronger than a 4L60E and there's all sorts of computer considerations with the swap. If you must go with an old-school tranny......go with a TH400; at least it's a stronger unit. But.....if I were in your position (and I have been), I'd have the 4L60E rebuilt!
2. Gears? Do 3.73's or don't bother! OK.....3.42's would be a nice step up for you, but IMO, the Impalas should've come stock with 3.73 gears (Yeah.....I know yours is a Caprice

) But the bottom line is B-bodies
LOVE gear......and your 2.93's are strictly for HWY gas mileage. On the whole, the 3.73's won't effect gas mileage much because what you'll lose in HWY MPG, you'll almost make up in city MPG (yep....3.73's will get better city MPG than the 2.93's

).
3. TC? Go with a 2800 stall Yank or Vigilanti......you'll want a 9.5" TC in any case. Going with a lower stall TC (2000 to 2600) will mean going with a 10"+ TC.....and those just don't take care of buisiness if you're really looking for a performance upgrade. A 2800 stall TC is the lowest stall you'll get with a 9.5" unit......and works great with a stock(ish) motor.
4. BTW.....one you have this work done, you'll need to have your PCM reflashed for the gears and TC. I use
www.pcmforless.com.
You have PM, BTW......
KW