I've built 4 or 5 400 block stroker motors with 4.25 crankshafts with both H beam and I beam rods and two 4.300 stroke crankshafts with internal and external oiling systems, on the five motors I used a stock 3/8 internal pickup I had to grind around .030 to .060 off the pickup boss near the threaded end to clear the front rod
Mock up the crankshaft in your block and install the front two rods and pistons with no rings on the pistons and check what grinding, if any,your block will need
The stock size Mopar rods need a lot more grinding with the steel H and I beam rods