For the 518, you will want to talk with the folks at SMR Trans and purchase some of their upgrade parts to do it right. I built an A500 with all of their parts, and it wokrs awesome in my hotrod.

For EFI, if you get tired of trying to work out the factory set-up, I would suggest the FAST EZ efi....Love it.

'70 Cuda,...605 EFI Hemi Street Car (6.20 best pass, 1.33 60ft)
https://www.youtube.com/watch?v=WYw6RA-k5Bk (6.25 at 108.75mph from inside car)
https://www.youtube.com/watch?v=3zQEb9uxFng (6.25 at 108mph from outside car)
https://www.youtube.com/watch?v=JCvfzsC4NgM (9.9)

'66 Barracuda AWB Stretched nose Blown 440 Car in build stage

'71 Duster Drag Car 400 Low Deck 512 best 6.002 at 115.44mph
https://www.youtube.com/watch?v=Znuo3jMUXTk