Hi Byron,
you can get them here for $4
http://www.kanter.com/p30-fon.html#fo12
I just called Mustangs Unlimited, a source the local Ford Dealership has referenced me to in the past, and Andy sqid he had them for the 390-427-428 high performance application, 9.56" long, at a cost of $1.95 each, #RP3172B
They also have the #RP3172, which is a 9.62" length.
Be sure you discuss the ball and cup design, versus the ball and ball design, as both were used in the FE motors, and you'll naturally want to order the same kind you have on the motor.
I'm not sure the length is all that important with the solid lifter motor runing at our rpm levels and with adjustable rockers, however, I would measure one of your straight pushrods and order the same length according.
http://www.mustangsunlimited.com/
Toll free 888-229-2929
Here is another source of info, but beware, becuse the 1968 automotive 427 was a hydraulic motor and we can't use that for reference. What we really have is a solid lifter 390, with a 427 bore (with the 427 block, of course), but with mild cam and 390 heads.
http://www.ford-fe.com/Pushrods.htm
http://www.gessford.com/cobraparts/fvalvet.htm
If you need a confirmation, let me know and I'll pull one out this eve and measure it.
Regards,
Paul