Here is some general information about boom blocks and eye straps.
Boom Blocks - Harken blocks are not allowed but the Race-lite swivel block, RL-221, is legal because it was previously provided by the Builder and it will handle 7/16 line. The swivel block is essential for the aft location to keep the sheet running free and it also helps in the forward location. The non-swivel block, RL-201, will suffice in the forward position if you have 1/2 inch more clearance for pulling the boom in "block-to-block". Blocks may be ordered from M&E Marine, Camden, NJ, at 1-800-541-6501. RL-221 is M&E Order #40643 at $3.85. RL-201 is Order #40644 at $2.60. The latest SLI blocks will accept line larger than 5/16 but are much more expensive and some binding has been reported.
Eye Straps - ISCA Class Rule 3.5.5 allows any type of eye strap to be used. The best strap is the Ronstan RF 498 because it is "U" shaped and allows the block to swing free without binding against the boom. M&E has it under Order #41151 at $1.82. The hole centers are 1 1/8 inches apart so a new hole must be drilled and the empty holes plugged. The Rules allow blocks to be relocated, so it is recommended that the forward block be located 65 inches from the front end of the aluminum boom to provide optimum alignment with the ratchet block mounted above the front lip of the cockpit, and to provide clearance to sail clip. The eye straps may be through-bolted to the boom using stainless steel bolts and cap nuts, which may be procured from Home Depot. Check the length needed and cut off excess length to accommodate the cap nuts, which should be installed on the bottom, against the eye straps. Use Lock-Tite on the threads to lock the cap nuts. Use tape or teflon to protect the upper spar from contact with the bolt heads when the sail is stored and transported.