New old '66 Barracuda

Before you get into tearing the engine apart, try draining about 1/2 the oil out and topping the crankcase back up with ordinary diesel fuel. Start the motor and let it idle 600 to 800 RPM, but DON"T rev it. After it reaches temperature, let it idle 20-30 minutes more, taking care it doesn't overheat. Drain the crankcase out completely and do a normal oil/filter change.
That original to the car 273 might have more life in it than you know.

"Back in the day" (early 70s), I rebuilt the original 347 in my '57 Safari (Pontiac for those that might not know) with 123,000 miles on the clock. Pulling it apart I found sludge 3/8" to 1/2" thick covering every internal surface that would normally be coated with a film of oil. Strangely enough, after hot tanking and measuring everything carefully, the engine needed only standard sized replacement parts except for the pistons needed to go with a .030 overbore.

Keeping the booster and going to the '73 and later disc brake setup with a split master cylinder would definitely improve the braking ability and make it safer for the daughter as long as you run an adjustable proportioning valve and properly set it up, but never owning an early A body I don't know how complicated it is to get the later bits onto the earlier body.

I'm so sick and tired of all the "new" paint colours and who ever came up with the idea that flat, oops, I mean "suuuuwaaaade" paint is something desirable ought to be shot on sight. I'm old enough to know that "flat black" paint was really dark gray primer and the first step on the long road to being able to have a nice, shiny, finished paint job.

If you "just gotta" change the paint colour from the factory original, dead straight bodywork under the smoothest, slickest, mile deep black paint ALWAYS wows 'em. Of course, at that point you might as well go the whole nine yards and redo the interior completely in smooth white or red glove leather.