Patience, Grasshopper- - - - -turn the cam until the base circle of the lobe is under the lifter, tap it down against the cam with a brass drift, and soak the whole works liberally with PB Blaster or KROIL. Repeat as required for all 12 lifters. That gets the lifters moving in their bores without having to pry or risk other damage. Once all the lifters are at their maximum upward travel the cam will slip out from under them. They don't necessarily have to be removed until later in the disassembly. Don't forget to remove the fuel pump and unbolt the thrust plate. it's accessible through the holes in the timing gear. The best "service manual" to have is a healthy dose of patience and common sense, no matter what engine you're working on. Stovebolt engines can handle an 80 overbore without any problem, but that would be the max most engine builders would attempt. Anything bigger requires "semi-finished" pistons that are ground to the diameter needed, and they are virtually impossible to find these days.
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!