Interesting. The stock on your newly purchased 1950 indeed looks correct for spike bayonet. The one on serial IM 349 doesn't.
Being a Russian sneak, anything could have happened to the stock on ИM349 between when it left Russia through its time in Albanian to when it was imported into the US. The scratchings within the S/N and date lettering seem a bit odd to me for certain. It may not be a 1950 stock at all, but it's been on that carbine a long long time. To me, the old number bears no resemblance to '349' either.
Being that we only have a population of 3 ИM prefixed guns from '50, we just have to compile the data as best we can and not make the mistake of making absolute determinations when the data simply isn't there to support it. Jstin2's carbine is certainly in the best shape of all 3. Maybe they all looked like that off the line? Maybe his carbine was a one-off? Maybe there's some other implausible but possible case we haven't even considered yet to reconcile the differences in the three.