You can replace them with 5/16 X 3 inch bolts but will end up back in trouble with the hinges freezing up after a while.
The above mentioned kit I carry was something I devised after being fed up with my own doors as well as many request from others to come up with a bushed design which would work for both function and future disassembly without the need of a torch and hammer.
The technical article I wrote for these is here
Steel Soldiers
After writing the article many complained that finding the mentioned bushings was more difficult than I anticipated and / or very over priced from what I mentored in the article so I put together the kit for the sake of obtaining everything easily.
If you are interested in purchasing the kit I do strongly recommend you FIRST READ THE TECH ARTICLE... This modification requires some level of know how with hand and power tools. It takes some "fiddling" and fitting to get just right but In the end you will have doors which open and close effortlessly with bushings that will last forever.
OD Iron LLC Military Vehicle Parts and Accessories Door pin kit....