75-76 Aluminum 833 4 speed Overdrive trans questions ?

I am running a 292 duration cam in one of the 340s. The other has a Comp Cams .468 270 duration solid. Both are high compression early 340s. I took one of the transmissions out myself so I know it came from behind a slant six but both have large spline output shafts. I think just running street tires is the key to them living behind 340s maybe.
maybe so but I broke three of them with street tires., one of them with a dead-stock 1973 318 with nothing more than a 4bbl and headers.