Repair parts shouldn’t be too hard to find as any 5, 5.5, or 6 horse piston from ’54 thru ’79 will fit right in although later pistons will use only two rings instead of three. A replacement rod might be a bit harder to find as it will have to be a 5.5 horse rod from ’54 to ’60. Later rods wont work as they used needle bearings on the rods big end and because of this they could use 24 or 50:1 fuel mix, instead of the 16:1 mix your motor requires.