a lathe with power feed works really nice for cutting thread, or just get out a die and cut your thread.
I'd think about taking an old rod and cutting it in half and removing about an inch of material out, then threading each end with like a 1/4 or #10 thread, then put a stud in between the two ends and use that to get your length.
1989 Firebird L03
1993 Thunderbird 5.0 HO
1995 F150
Gonna be building a 351 Boss this summer!
Summer's over, never got to it...
This is my current build though
http://www.302w.com/Forums/forums/thread/1100.aspx