Wow! Thanks for this information! My car is a 1960 101 Veloce.If you are running a 1300-101 engine and split case 4 speed transmission, odds are excellent you can use your existing transmission crossmember and spacers for engine tilt. The later 101-1600 Veloce specific mount was designed for the increased torque of the 1600 over the 1300.
That said, some transitional 1300's may have the smaller diameter tail housing silent block mount, and that may be 4 speed specific, I'm not sure. If your car is a 750-1300 with tunnel case, you need to do more work as the hole in the chassis for 750 is smaller, and further to the rear, so body work is needed though there are many BB owner 750's converted to split case 5 speed transmissions.
For a 101 1300, the 4 speed and 5 speed cases and dimensions are identical, so it's just a transmission swap, you can even keep your 101 1300 bell housing with the window for timing marks, just bolting in the 5 speed. You must note there are some differences with 5 speeds, and the one you need has the shift rods that protrude from the case front to activate the R light switch. Later 105 5 speeds transitioned to no rods through the case, a different R lock out and a different input shaft size, requiring a special oil seal if the 1300 101 bell housing is used.