The Merc 410 used a C6ME or C6ME-A 390 block with a IU 428 3.98 stroke crank. The 360 also shared the same block as the 390 and 410 and all have a std 4.05 bore just the crank stroke difference. The C6ME or C6ME-A casting number is on the right side of the block. Depending on which 427 rods you have will determine the value. Tell me the numbers on the side of the rods. The IU crank in worth maybe $400 at .030 on mains/rod journals. The C6ME and C6ME-A 360/390/410 blocks are plentiful and maybe worth $500-600 max if still std bore and good shape. Depending on what rods you have you might break even on your investment. What is the date code on the block? It's a number/letter/number(s) sequence below the oil filter adapter mounting pad. On the small angled part of the block there.