Quote:

what I would do is run a drag/street tire of 30 inches hieght and run 391 or 410.



There's about 3 rpms difference at 70 mph when comparing 26" tires with 3.55's and 30" tires with 4.10's (this happens to be the combo on the GTX) Here's a decent online calculator which makes it easy to compare options...

http://golenengineservice.com/calc/calcrpm.htm

'69 Plymouth GTX
See you on the street...