I ended up using studs. It worked remarkably well. I was able to find the perfect lengths of studs to replace each bolt, with the exception of the lone short bolt. That one required 2 washers to make it work:
It was surprisingly not too expensive. I already had the appropriate 3/8-20 nuts and 3/8" washers on hand, so it was just getting 9 individual studs (2x 3.5", 6x 2.75", 1x 2.160"). If I could find a 2" stud instead of that 2.160", that would've been perfect, but the longer one works fine with the extra washer.