Tell me about this 273 and tranny.

IMHO the dust on the outside is also on the inside.

With no blockage over the intake likely mice / rats nests in the intake or a cyl if a valve is open.

Same for exhaust.

If it is super cheap it might be worth it.

But by super cheap I mean 100 to 200 bucks

273s are expensive to rebuild due to the pistons.

If it has early heads, the heads on the intake manifold bolts will be smaller and at a different angle then the later heads (making them less desirable, but not a deal breaker,)