I have done the stand offs and the chamfer method on my first Big Bore"race" engine. And on my last one I did neither. I think it is a good bit of work for an unknown amount of benefit. I did drill an extra hole over the fuel pump, and I ran a wheel cylinder hone through the lifter bores to give them a little extra clearance.

I believe the standoffs I used were 3/8" pipe nipples(brass) that I cut in half and then threaded down into the block. I made my own tool to thread them in. I'll see if I can locate a picture for you. There is not much room to work down in there. But you can put your 3/8" NPT tap on a long extension with a socket and tap the existing holes. Obviously any additional holes you drill will need stand offs put in also. There is also a hole in the front off the block where the oil will run out onto the timing chain once you put stand off in. I tapped and plugged that hole with a flush aluminum plug with an allen head in it. Then I drilled a small hole(guessing 1/8"or so) to allow some oil to get through there.Not sure if that was the right thing to do but that is what I did.