I have the stock (7.8"?) rods from another 350.
the 'details' say "The use of retrofit lifters may require the use of special length pushrods"

I put the parts toghether as you say - and without collapsing the lifter and the stock length rod allows the rocker stud/nut to go one about 1 to 1.5 threads - and there is no clearances at all (as i expect there should be with the valve on the seat and the lifter on the 'heel' (base circle).

Rods can be had .5" shorter, in .1" increments.

perhaps take a stock motor (have a 305 laying about) and measure ho far the stock rod protrudes above the head or some such place and try the same distance measurement on the fortec motor?

i don't have the summit receipt in front of me, but we got there version of edl-97383 - the edelbrock lifters. the edelbrock ones are not in stock, and the summit ones are $20 cheaper and 'the equivalent' the sales weenie said. crane makes the same thing as well.