Remember too there were around 10,000 or so Kaiser Specials built during the 1948 model year with Custom interior upholstery and trim. The factory sent a memo out to dealers on this so they would not get concerned that the line screwed up. The memo doesn't give a serial number range but based on dates in the document it looks like May-June or so of calendar 1948 for production.
The next release of KFOCI HANDBOOK has the info I have gathered so far on this; right now, all my stuff is packed up for the move to Washington state.