Have a T5 hanging behind a 235 in my '60 C10. O.E. mounts, 1 at frt of engine, 2 at sides of bellhousing. Ran a muncie M20 for 18 years before this trans. No rear mount, no problem. The general built these rigs with 3, 4 and even 5 speeds hanging off the back and if you've every pulled a Spicer, New Process of Clark transmission with the park brake you know how heavy they are.
