Don't forget that you'll need to also swap over the distributor. The head-mounted distributor (as used in the later 740) won't fit in the 240.

While you have the motor out, BE SURE to install a new rear main seal.

The front seals you can do anytime, although it wouldn't hurt to also replace them now.

If the gaskets aren't leaking, don't touch 'em -- particularly the head gasket.

Flametrap is a component in the crankcase ventilation system. Its purpore is to pass the crankcase gasses to the intake manifold but to block any flames, such as might occur in a backfire.

A turbo motor has all the plumbing but lacks the actual flame arrester element.

The flame trap assembly is located between the 3rd and 4th intake headers, tucked down low and tough to access. The flame arrester element is a disc about 1" diameter and 1/2" thick and sits in the black plastic "Y" fitting. The old style was brass mesh; the new style is white plastic -- a thick disc with many holes.

--
Don Foster (near Cape Cod, MA)