sounds like you may want to see another machine shop if there talking a stock length rod ? you can use a 4.250 crank or 4.375 or 4.500 crank are ez to get in the 10.200 deck block .i would use a 4.500 crank .you could even use a 4.750 crank with a 6.700 long rod and a ch of 1.120 piston longer rods help with more counter weight on the crank .then longer rods help with getting the pistons to clear when they come a round less your looking it a cast steel crank i would build it bigger then a 496 it will be the same to build as a bigger stroke crank