Engine replacement for 62 Nash Metropolitan

Is there any new or newer rebuilt engine that can be installed in a 1962 Nash (AMC) Metropolitan that requires little or no modification?

I recall an ad in the back of HOT ROD many, many years ago for a modified Olds 370 (late 1950's IIRC).... and an Olds rear end narrowed to fit a Nash Metro. :eek:

I recall the 1500cc Metro motor being Austin, there might be a bit o' research but I'm thinking perhaps an MGB unit bolting up. :2cents: