727 to A518 swap

This is a really great swap, so don't let a lil thing like lack of it being a bolt-in, deter you. That .69overdrive lets you run just about any rear gear up to about 4.56s in a streeter.
as you probably know 4.56s x .69=3.15 final drive, and AFAIK all 518s have a loc-up.
With the starter gear of 4.56 x 2.45=11.17, you don't usually need a stall.
Typically tho, on the street, the A518 is run with 3.91s, for a lil longer 9.58 first gear. However this brings the Final Drive down to 2.70, and so 65= about 2185 by the math.
If you are installing this for fuel economy AND installing a longer period cam, you may not be able to give the engine enough ignition advance with the factory-style distributor, to get the fuel economy increase that you might be expecting. To cruise at 2185rpm, the engine has to making strong torque, so that it doesn't need a lot of timing advance.
I got that torque with 11.3/1 Scr, and a [email protected] cam*. But with the pressure pushing 190 or more psi, I went with Alloy heads to not get into detonation under power. At that time I was cruising at 65=1600 with a manual trans. It got phenomenal gas-mileage.