If your getting a little too enthusiastic in rod to block clearance and get a pin hole in the coolant passages, Id use a 1/2 cup of J&B epoxy weld (basically both full tubes mixed and poured into the coolant passage )
poured into the blocks previously carefully steam cleaned and heat gun dried coolant passage area
Ive seen it done several times in the last couple years without issues
the tall deck block requires a longer reach distributor shaft thats about 0.28 longer
thus the need for the adjustable collar on the distributor adding the extra reach to get the oil pump drive and drive gears to properly align and mesh.
be aware theres an oil supply passage in the lower block skirt, and coolant passages that extend quite low on the mark IV blocks so you can't just grind excessive rod clearance, for crank counter weights and large, longer stroke , stroker type crank's to the same extent you can get away with on the later MARK V and VI blocks, or the far better choice of a DART aftermarket block, so you'll need to be careful,doing clearance grinding,I would advise limiting stroke lengths to a 4.375" max, even in the tall deck truck MARK IV blocks, the later Mark V and VI blocks have that passage up near the cam tunnel
if the grove youve cut for stroker rod clearance in the lower bore skirt is in error so large it starts to drip out coolant or if its cleaned and inspected you need to make repairs in that area the proper J&B epoxy will permanently seal the coolant passages, you can prevent epoxy from dripping out before it sets up and bonds with a temp plug with plastic clay, every decent machinist I know has a package to measure some clearance like oil pump pick-up to oil pan floor and valve too piston clearances.
WEARING A FULL FACE SHIELD and having a 5-6hp shop vacuum set up to suck the vast majority of the debris from the porting work out of the air is going to help prevent some accidents and getting crap in your eyes,
THIS vacuum, is THE ONE I PURCHASED AND I RECOMMEND IT,
remember to change filter elements frequently and a couple quarts of water and a couple drops of dawn dish washing liquid in the water traps a great deal of dust in the lower body before it gets to the filter, place a 2" pvc pipe extension too the opposite end of the cylinder head port or as close as you can to the area your grinding, that your working on with the burrs and die grinder, and duct tape it in place, the vacuum will control and limit much of the machine debris
http://www.homedepot.com/p/RIDGID-16-Ga ... 5yc1vZbv79
there are some good die grinders on the market, but these less expensive import versions, are a BARGAIN even if they only last for a few weeks or months,under constant use they do wear out in a few weeks or months (especially if you fail to used dry air and don,t bother to lube the tool.) because wet air and moisture tends to cause internal rust/corrosion over time.
OBVIOUSLY dependent on the amount of use and abuse, I use mine almost constantly for cleaning and porting, de-burring etc.
but at under $20, I tend to look at them like sand paper,or spark plugs, its hardly worth bothering if it lasts a few weeks or months before the bushings start to wear noticeably
clean any block you buy and look for obvious cracks and if you have doubts get the machine shop to mag or dye test the block or heads
and lifter gallery
,piston bore walls,
block main cap web support areas
heads between the valves in valve seat area
look for stripped head and manifold and oil pan mounting bolt threads,
in threaded holes and cracks in block radiating from the holes
ASK LOTS TO QUESTIONS & SHOP CAREFULLY,