4L60e or TH400?

Ok so with my new found power, Im kind of worrying about my slightly built 60e and circle d 3C. It runs and shifts absolutely perfectly but I dont want to wait till one or the other gives out to do a swap because if one goes then both are going to be practically worthless. So should I be really worried as much as I am? Im looking to push it to around 650rwhp and want to be 100% confident that my tranny and stall will hold. I talked to my tranny builder and I he said he has a few turbo 400's at the shop and will build one to the max for me for only $900, that includes the tranny and rebuilding it and he is really good. I did a little research and it looks like I will need to get a new flexplate and im looking at the TCI unit which is $230. I will also have to get a stall capable of 800-1000 hp and Im still confused as to what brand and what style converter, SBC or retro LSX or what. Im wanting to go with the 400 rather than a 4L80 because its easily 65lbs lighter, way cheaper and simpler. Im also throwing around the idea of a transbrake but im not sure yet. So what do yall think about me doing the swap and if anybody has already done it can you please lend some advice.

get a neal chance convertor. Call them and tell them your application and they'll build you one mean mother convertor.

Thats one of the companies my tranny guy recommended! Do you have a 400?

nope, 4L80e and run a precision industries 3600 vigilante convertor custom built to fit a LSx flexplate. I like having overdrive even though I run 3.23 gears. Low RPMs means less oil vapors plus turbos love numerically low gearing.

Yea Ill also be swapping the 4.10s out for some 3.42s.

With the TH400 my main concern would be the loss of overdrive. I drive my stuff around too much to do with out. If you wont have that problem then go 400

Yea, ive thought about it and Im not too concerned about it

4l80 vs th400 isnt much of a weight difference

Its a street truck. A 400 weighs about the same as an 80e. I'd do 80e all the way.

400 is lighter but not that much. The benefits of having an overdrive outweigh the added weight. The convertor is where a lot of the added mass comes from on an 80e and if you're getting an aftermarket convertor then you can reduce weight by getting a 9.5-10.5" converter to drop about 35 lbs during the conversion.