No need to replace head bolts each time unless the company that sold them to you specifies that they are use once only headbolts. I have been using the same exact headbolts that came with my truck in 1986. If you purchase the headbolts with the original allen head design, no modifications need to be done. If they are not the allen type and are the hex head, some modifications need to be made so they do not interfere with other parts of the engine cover or rocker assembly.
When using headbolts over, be sure to replace them back into their specific homes within the head. Try not to mix them up if possible.