I'll be using 1/2" flange nuts & bolts to install the main frame crossmember replacement on my '46 1.5 ton...but...the argument I got from an engineer friend (ex-NASA) was that hot-bucked rivets form a completely different type of attachment. Because the rivet expands to fully fill the holes as well as compress, it will transfer any structural load across the opening as if there were no hole. A bolt, no matter how snug fitting can only apply compressive force. In other words...anywhere there is a hole with a nut & bolt, the material is compromised by the removal of that mass. But a properly formed hot bucked rivet will act as if it is part of the surrounding mass.
He used a lot of much bigger words but that's what you get when you talk to rocket scientists.
Like I said...I'm still going with big [censored] bolts.
