commercial vehicles have a higher limit for capacity increases.

for a datsun 1200 sedan / coupe / wagon the limit is about 2250cc NA from memory

for a 1200 ute i think the limit is 2.6L-ish - this is remembering a while back now so excuse me if it's wrong but you get the point yeah? under these rules, a "2.4L" 12A is right at home.

ring around. i think you'll be pleasantly surprised.