Just pull a lifter or two and use an inspection mirror to look down the hole. A drilled block will have a large hole running front to back about halfway down the bore for the oil supply to the lifters. You will still have to change the camshaft, even if the engine block has the oil gallery drilled for hydraulics. Hydraulic lifters simply will not work right against a solid lifter cam.

The line under the pushrod cover is original- - - -aftermarket bypass lines are installed outside the engine and get plumbed into the cylinder head for oil supply to the rocker arms if the internal lines and/or passages get clogged up.
Jerry


"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!