Ok...This ought to stir the pot...

I remember very few custom pushrod mfr.s back in the day-like you say, it wasn't something we worried about. And when I did need a different length pushrod for those 273 rockers, we just scavenged some slant 6 pushrods, knocked the end off, cut them to length, and pressed the end back in... I think they were larger diameter, too... Instant heavy duty, custom length, and basically free.