1) You will need to get an adapter plate that will mate the Allison trans to the small block Chevy. These are available from a number of different manufacturers, so you should be able to find one that fits your needs.
2) You will also need to get a flexplate that will fit the small block Chevy and the Allison trans. Again, these are available from a number of different manufacturers, so you should be able to find one that fits your needs.
3) Finally, you will need to get a driveshaft that is the correct length for your application. You can have a driveshaft made to your specifications, or you can purchase one that is already the correct length.
Once you have all of these parts, you can then bolt the Allison trans to the small block Chevy and start it up. You may need to make some minor adjustments to the shift linkage and throttle linkage, but otherwise it should work just fine.
