"3650" means 360 tq and it's a 5-speed. This is from a Tremec rep I talked to at a Fun Ford event in Bristol. If that's the case they should of named it a "3605" in my opinion, but that's not important.
I twisted my input shaft and took out some synchros with 400rwtq on 17" BFG drag radials barely hooking at all. So I'd say Ford's rating isn't too far off.
My stock 110k mile T45(similar to the 3650), has 10 years of use, and over 50 passes at the drag strip, launching between 4500-5500rpm. Daily driven car over 220 miles/week. I do not powershift. Royal Purple Synchromax fluid.
I was making around 375rwhp+ same Tq for a while now, and havent had an issue. Stock Clutch as well.
I am getting my new tranny/clutch shortly, but wont be able to put it in until AFTER I pick my car up from my engine builder. So I will be making well over 400/400 with a stock 3650 and stock clutch for a day or so. Luckily I dont have to go far, and I dont plan on beating the piss out of it for the first miles anyway. As soon as I pick it up, Im driving it home and installing the new transmission.