[rotorwrench]

Having worked in an industry that still uses studs for a lot of engine applications, I can see why some may have a need for a stud-like bolt. Stud applications were and still are used as a way of controlling the torque up of the complete fastener system. The studs were generally always installed at a tight thread fit fastener. In other words, they weren't tightened till the threads bottomed out. They were tightened for a specific torque level depending on how tight the thread fit was designed to be. Some but not all applications go into bottomless threaded bores such as water jackets and the like. This allows for a better seal in those applications and in threaded bores that do have a bottom, they were generally in high temperature applications where loosening may happen from constant expansion and contraction of the related parts. Alignment to prevent fretting is also a factor for stud use but it's not the only reason for their use.

Then a stud bore was found to no longer meet the torque up specs, oversized studs were used to restore the tension required for torque up during overhaul or repair. Due to the age of the average model A engine and its likely history of repair and overhaul, it's doubtful that all of the original stud applications will still meet the original factory specs for fit. Although a bolt is not original, it doesn't need to meet the fit up requirements that most studs would require in order to take the fastener apart without the whole stud coming out with the nut.

In the modern era, we have stud locking products that will work to hold studs in place in many cases where the stud is somewhat loose in fit. It just depends on the condition of the applicable casting. A lot of stud information has gone by the wayside over the years and .003" or larger oversized studs are no longer common.

If a person cares about originality the the studs are the only way to go. For those that are marginal on that subject, you can use a bolt or one of these faux studs instead.