There is no need to interchange any components from a different transmission into a TH350 to make the transmission stronger.
A relatively basic TH350 build with decent frictions, Kevlar intermediate band, Teflon sealing rings, a heat treated intermediate sprag race, new intermediate roller clutch, new low/reverse roller clutch, properly rebuilt front pump, and TransGo shift kit will typically handle 500 flywheel horsepower in street and mild street/strip applications without any issue.
Add a 36-element intermediate sprag (requires special machining to direct drum) to the above build and a TH350 will handle 650+ flywheel horsepower depending on how it's going to be used.
Add a billet input shaft and low/reverse roller clutch support and you can throw upwards of 850 - 900 flywheel horsepower at a TH350, again, depending on how it's going to be used.
At elevated power levels it is usually a good idea (although not always necessary 100% of the time) to install a full manual valve body or transbrake valve body. The full manual and transbrake valve bodies will allow the use of slightly higher line pressure which will increase the holding ability of the clutch packs.