Holley needs to fill in some gaps, they go through all the trouble of making the engine fit, but then their efi system has no nag1, 545, or even 46rh, or re control. Go through all that swap to end up with np435 or 727? How about a Nag1 to right hand drop np205 adapter? What about accessory drive and alternator control?
May as well just stay with sb or bb and efi it.