Here is some technical information from the QA1 site that you might find useful. The first link describes how a rod end's ultimate static load is computed -- it is the lowest of three areas: race material compression strength, rod end head strength, or shank strength. The second link provides a cross-reference of various QA1 rod ends to other manufacturers (Aurora, Spherco, etc) which might be useful when comparing prices.
http://www.qa1.net/qa1_industrial/ra...ad_ratings.pdf
http://www.qa1.net/qa1_industrial/part_interchange.html
I have attached a shot of my garage-built 4-link for an independant suspension. It uses a C-4 Corvette upright with Woodward swedged tubes and Aurora rod ends (3/4 in.).