Wally,
Just to be clear, since you have re-numbered the gears from the standard designation, you are doing a rolling stop from what you call 2nd gear (what most people would call 3rd). Since the SM420 is synchronized in second gear (which you are calling 1st) why don't you use that gear? It should slip into gear easily, the engine is in a range that will allow fairly rapid acceleration (unless loaded going uphill) and avoid shuttering, and avoid the whole question of whether it is harmful to the engine. Unless we did a randomized blinded controlled study you will only get opinions, which few of us can back up with relevant facts.
Let's see, to do this study we would take 20 random brand new 1948 3/4 ton trucks, drive them for two years as you describe and then take 20 similar trucks, drive them for two years as I suggest, and then have Hotrod tear down all 40 engines (in a blinded fashion, meaning he doesn't know which truck belongs in which category) and then report back to us his findings.
Just kidding, of course but I am curious about why not drop into the gear just above the granny gear, unless your synchro has worn out.
Regards,
Kent
