Tough one...late 60's maybe 67 but it was either a Revell P38 in 1/48 ..
Revell didn't make a 1/48 P-38 kit.. Mongram did, but Revell's offering was that monster in 1/32 scale.. That WAS a big model! Huge for a kid.. Had to have it then too, lol.. I'll probably finish it in a couple more weeks, lol..
The current 1/48 Revell Lightning is the former Mongram kit..