[Excaliber]

I think were missing data on what TYPES of roller cams are available.
Hydraulic rollers are more reliable than solid roller for the simple fact that the ROLLER BEARINGS get more lubrication than a standard solid roller. It's the ROLLER itself that fails. Today there are special roller solids that DO get enough lubricration to survive on the street, but the 'package' required to get it right is much more expensive than a standard solid roller. Standard solid rollers are NOT recommended for street use, they WILL fail well before a flat tappet or hydraulic flat tappet or hydraulic roller.

Some FE's are NOT set up for hydrualic lifters, period, you cannot run a hydraulic lifter of any type. From about 68 on FE's were drilled for hydraulic lifters and you can run whatever you want.

I would be tempted to go with a hydraulic roller lifter in a later model (68 on) FE block and wouldn't think twice about it, IF thats what I wanted. I think the advantage (more aggressive cam profile compared to flat tappet, generally speaking) may be worth the cost for some. Unless you get a really good hyrdaulic roller setup ($$$) you will be limited on rpm compared to a flat tappet.

Me? It is NOT worth the extra cost, and the cost can be a LOT more than flat tappet! I broke my solid roller cam in about 8,000 miles (roller failure) and went with a solid flat tappet for a couple of reasons.
1. Thats what it was 'back in the day'.
2. Saved a bunch of money (my block WILL accept hydraulic lifters).
The issues with premature flat tappet cam failure are easily addressed and it is NOT an issue if you pay attention to the installation and break in procedures currently recommended.