The key thing required for an FE block is hydraulic lifter CAPABLE. The early blocks were not drilled for
oil passages to the lifter, solids were the only option. Around 1968 or so they were drilled, in that case you could run either.
I'm pretty sure any modern after market block is also drilled to except either solid or hydraulic. You DO have to modify the
oil gallery to the lifters depending on which way you go. Restrict
oil if solid, increase oil if hydraulic, simply screw in the right size restrictor. A small but very important detail, which could easily be over looked by those not familiar with an FE block.
Stock E-brock head springs aren't matched to any specific cam profile, there only 'in the ball park'. You WILL want to buy a 'cam kit' (springs that DO match) and install the springs in whatever head your running.
I had a solid roller in my side oiler, it went belly up at about 8,000 miles. MAN was that a strong motor! Great on the track, nightmare on the street, no power below 3000 rpm. I estimat I gave up about 150 horse power on my rebuild, down from 667 to say 500 or so. Lowered compression, smaller carbs, smaller flat tappet cam, etc.
Now get this:
Loosing 150 horse resulted in loosing only a few hundredths of a second and a couple of miles per hour in the 1/4 mile! My gas mileage DOUBLED, streetability vastly improved and the car STILL runs in the 11's. BIG horse power doesn't mean squat if you can't 'hook it up'.