That's a great question and the general consensus is yes, you can use the used bolts for the plastigauge.
The manual says to buy 2 new sets of rod bolts and to chunk the set you use to measure.
See if this shoe fits, measure them with the used bolts and if they measure way out of spec, try with a fresh set of rod bolts. If they are in the window, call it good.
Basically, if you have the stomach for it, use the used bolts. If you don't, don't.
Another option is to buy a set of arp bolts and use them to measure and then reuse them.
The manual says to buy 2 new sets of rod bolts and to chunk the set you use to measure.
See if this shoe fits, measure them with the used bolts and if they measure way out of spec, try with a fresh set of rod bolts. If they are in the window, call it good.
Basically, if you have the stomach for it, use the used bolts. If you don't, don't.
Another option is to buy a set of arp bolts and use them to measure and then reuse them.