I just sold a Model A with a 181 Mercruiser 4-banger/4-spd. Not an oldtimer, like yours, but I had a blast with it.
I'd love to have a Model A, or B engine with an overhead conversion and a pair of Windfield carbs. Nothing sounds better than one of those big old bangers.....bet yours sounds good, too!
With a modern transmission and rear gears, that sucker would still be a lively performer.
Hope you opost some more photos of your car!