I've had a lot of luck over the years with the factory non-adjustable rockers. I have them in a lot of engines, all at around 150-160 seat and 375-400 open pressure, with lift hovering around the .600" lift mark. Dennis Towle has them in the 540 hp 390 that I built for him. That engine has almost .600" of lift, 170/400 lbs of spring pressure, and he absolutely beats on that engine. It's been cruised, it's been street raced, and it's had innumerable passes put on it at the strip, launching at 5000-5500 and shifting at 6500. Obviously, the rockers work well, even with their flaws. However, with the higher rpm hydraulic rollers that I've been doing (6500-7500 rpm), I didn't feel comfortable with the factory parts (lack of structural integrity with high spring loads, wider footprint on the stem, etc.), which led me to look at some aftermarket pieces. I approached both T&D and Manton about making some steel non-adjustable rockers for me, but after some careful consideration, I decided that the budget just wouldn't be there for most guys unless it was a true race piece, and a true race piece deserves more than a traditional shaft mounted rocker system.
I agree that less moving parts can possibly provide for a better scenario, and in the case of an FE rocker, removing the adjuster from the back end of the rocker helps in a lot of aspects. Not only does it remove a failure point, but it reduces weight off the rear of the rocker arm. A bushed fulcrum can also add longevity, although the LS guys are all putting 100k miles on the upgraded needle bearing trunnion rockers. The roller tip isn't really a big deal to me as I can't remember the last time I've seen a roller tipped rocker fail, with the exception of a set of Procomp roller rockers. But there's a difference between a set of rockers made by Playskool and true, quality parts. With the FE heads all going to at least an 11/32" valve stem diameter, not to mention 5/16" and 7mm, we're losing real estate to center a shoe tip on. I have a couple of guys who put 5000-6000 miles per year on their FE with T&D streets, so I have faith in well-made products.
Obviously I'm biased, but I think the most important selling points of my rockers are that they will oil in either direction (through the head or through the pushrod), you get a little more rocker ratio than with a factory non-adjustable piece, and they don't use any funky pushrod ends. Buying a set of custom pushrods with a 3/8" ball on one end and a 5/16" ball on the other can get expensive but a 5/16" or 3/8" diameter, ball/ball pushrod is available from almost every pushrod manufacturer for about $100-125 in .025" increments. When I set up a set of non-adjustables, I will measure each valve for its own pushrod, as there will always be a tolerance stack between valve dimensions, valve jobs, etc. I then add .050-.060" of preload in most cases with standard travel lifters and order the pushrods to fit.
