High RPM shifts, W58 or R154?

[GST95]

I dont own a Toyota, but am considering a few different trannys for a mitsubishi 4g63 powered rwd project. The 2 toyota ones im considering are the W58 or R154.
I cant seem to find the info that I need about these trannys, so I hope you guys can help me out or point me in the right direction.

I dont need to know if it wont or will work. What I need to know is what is the max rpm I will be able to consistantly shift both of these?
I know the R154 is stronger. I read on here that the W58 can hold up to around 400whp, and the R154 ive read different limits from 600-1000. I think either of them will hold the power from what ive read, but the W58 might not last as long.

The engine that will be used will probably be around 300-400hp and rev to 7-8k maybe more.
Do you think either of these trannys will work good with these specs, or should I look at my other options?
If there are any other PROs or CONs to either of these please let me know.

I think I already have a W58 (out of a 84? celica). I would like to be able to use it, but if it wont hold up Ill have to find a R154 or something else. Is there any identification marks on it to verify that it is a W58?

Thank you for your help.