done many bbc in 4.250 that i know it more then 4.000 i built over the years and many 4.375 .rod works at 6.385 no need for more rod in the 9.800 deck block any more the pistons start getting short and ring pack start getting tight for space as the wrist pin is in the oil rails. with the 4.375 crank there not many making the pistons for that stroke less it a 14to1 a race pistons. i use the 6.385 is a shelf rod evey one makes this size rod and can come many ways in Ior H and in forged finish like stock rods for the street you still can get a piston with a good ring pack. or the 6.535 rod with a 1.070/1.065 piston ch wiseco makes them but a race piston hi CR . a K1 rod they make off size rods and work with a shelf piston like 1.120 ch but word need a rod around 6.500 long and i think makes 6.410 /6.420 long then 1.180ch piston i di not have my K1 book here but you get the ideal . the best bet is with a 6.385 rod with a Ch of 1.220 now in a custom made piston. that will get you 511 CID but there abit of work . Mahle makes a piston with a small dome but most companys make the piston with a bit less Ch on the piston so you can deck the block. old stock blocks all should be deck. if you tru-deck it. like i do .you can find your self taking abit more off to get the block true .so most of the time its not hard to be at 9.790 or 9.780 . most all the time its not a big deal and piston companys have this in mind . but not Mahl . i have talked to them asking to speak to the dumb ass that made a piston that works only on a 9.800 deck block. no room to clean cut the block and you can forget about a tru deck as when your done you will be looking for a head gasket 060 thick this is not the way i like to do things. so they pushed this screw up on there bbc piston on the eagle as they told me they made them for eagle so i talk the them trust me i save some time on the phone after taking to them clowns i think they such my brain matter out when i was on the phone .but mahle sell it to any one it is not proprietary to eagle? this piston is the only piston they offer built with no room to clean up the block . so do not buy the mahles i will say they do make nice pistons but some one truly someone head his head up is ass less your not going to do any work and if you fine the pistons hanging out of the deck your going find head gasket s at 100. bucks side and you need to make sure the crank counterweights are cut for the 6.385 rods you should use a cap screw rod as with a threw bolt rod there will be to much bolt hanging out of the rod and that is more cutting on the block to have the rod swing threw the crank case . now the 4.250 cank just about drops in and i done many of the 4.250 cranks with a 6.385 rod every one makes pistons for them it just the way to go . know what most guys thing two bolts just will not hold up and i must need two more to make my world right this is plane bull shit . the bbc bottom end is one of the best built and one of the better oiling blocks it.s not a sbc the main caps are 1/2 not like 7/16 that sbc are .and the big block as a 6.135 rod stock they been some test done i built longer rod bbc most all the time i was looking to hook the piston to the rod the longer rod engine would be very hard to see any gain and go threw the work to find the power on a longer rod engine