Here is another neat stovebolt page;
http://www.chevrolet.com.au/articles/engine_swap.htm

And a quote from the above web page about hydraulics:
"4. Let's solve the "hydraulic or solid lifter question" now... "Solids" were the rule on every Chevy '6' through 1949 (either '216 or '235 "Loadmaster"). Between 1950 and '57, solids came with every commercial or "stick" (pass.) transmission, whether '216 or '235 or '261 engine. Hydraulics went only with PowerGlide equipped cars. From '58 to '62, every block was drilled for hydraulic lifters, though some had solids installed. Hydraulic lifters will only function in a block that has the oiling passage drilled through the lifter bores (which hole will be plugged and visible on the rear of the block, just above the cam plug). "

mike in tucson