Of all the 69 L48's in the database (over 800), only five have 186 heads. Of that, one is mismatched (one 041 head and one 186 head), two have question marks beside the entry and two "may" be original. Of those two, one is a LA car from mid November, 1968 and the other is a Norwood car from early February, 1969.
Now, of the other L48's we have, there's not a lot of info on heads, but 30 of them have 041's.
Ed