hardness of backhoe pins and bushings will grade 8 work

Have to replace a pin on my dozer. its 3/8 and a foot long. case wants

300.00 for it. Was thinking of replacing it with a grade 8 bolt. If I recall grade 8 bolt has a hardness of c35, and pin is c55 or more. is the rockwell hardness linear? What other factors should be considered?