A500 or 727 with GV?

There is no big block version of an A500 either.

Just do some research on what a 727 needs to handle the power and you will know what you should be doing to the A518. Also, it makes a difference in what you plan to do. If weekly trips to the track with slicks and other traction aids it will take a lot more work to get it to handle that. If its just a street car with street tires that might occasionally see a trip to the track a stock rebuild would likely be adequate.