Thanks for the help D.Hearne! I may need more from you in a minute...
347Fastback, I searched the ID for "RUG-AD" and it says on www.4speedtoploaders.com that it is a "1968 Mustang 390, 28-spline, close ratio" transmission.
I have a 289 now and will be upgrading to a stroked 351W in not...