i have a 1971 413 from a winnebago i bought to put in my 69 charger, i want to put a 6-71 on it eventually. i know the block is stronger than a regular 440, thats why i got it. anyway does anybody know anything about these engines? comp ratio? what would the max SAFE overbore be? is this a 4 bolt block? (i cant look at it, im in cali its in utah) how much hp can the block/crank handle? are the pistons good enough to handle a street blower? or who makes pistons for it? sorry for all the questions but i really know nothing about this engine, all help will be greatly appreciated!!!  

Well it's a small bore 440 basically [4.180 as opposed to 4.32] .
Factory compression is any where from 9.2-13.5.[max wedge]
Better get some forged pistons for the blower idea.
Block and crank[a lot of the 413 cranks were flame hardened] can handle 650 or so hp.
LY rods around 575-600 and this can vary depending on RPM, comp,piston weight.
Pistons are made by any high end manufacturer like ross,diamond,wiesco, KB, ect.
Safe overbore up to 4.24 or .060 over, If you sonic test it yo might find a lil more room.