Ok I'll splain it to ya...
The lifter bores are not true enough for long term roller rockers.
The lifter bores are not deep enough either, especially for high lift rollers. So kinda negates having a radical cam.
Yes you can get lifter bores bored and sleeved with brass, actually extending the brass higher than the block to give more depth
to the bores... but you need a race engine builder to do this. This equipment is not standard fare in automotive machining.
Because of the slight miss-alignment in the lifter bores, the rollers themselves will start to umm. .. loose their **** and galling occurs...
which pollutes the engine with micro (and eventually macro) pieces (flakes) of hardened roller face steel.
These old engines as awesome as the oiling system is, is sub standard for the rollers resulting in... the needle bearings (in the rollers)
giving up the ghost. They are more happy with race engines (but you can't run really high lift cams anyway so moot point) with radical
cam that has a higher idle speed than a daily driver. yes you can buy Redline lifters with bushings instead of needle bearings BUUUUT...
look at the price and **** your pants.
A lot of extra expense for only a very slight boost in performance. Read this sentence over a few dozen times.
Oh and I didn't mention the cam button details... they are not reliable.
Retro roller cam manufactures suggest you inspect every 3000 miles... eeesh.
Fogetaboutit if you want to run propane. Propane engines like to idle down to 500 rpm. Your roller lifters will be having a fit with
oil starvation.
Retro rollers are for hot rods, mud trucks (with 3" body lifts) and anything NOT a daily driver.
Going to retro rollers because you're afraid to break in a flat tappet means... you must not have heard of grooving the lifter bores.
You want to free up some hp? Use an electric fan.
I know, it sounds cool to say "yeah Bubba she's a full roller engine".
Again, it's a very large financial investment for only a very small increase in performance.