The tube at the bellhousing area is a vent. Just be sure it's clear. Has the original crossmember been removed in the bellhousing area of the frame? If so, there's going to be an issue with frame flex at the rear of the front springs. It's usually a good idea to replace that piece with a dropped-down piece of square tubing that has clearance for the transmission and still stabilizes the spring mounts.

If the stamped engine number ahead of the passenger's side cylinder head has a "T" in the suffix letters at the end of the number/letter sequence, the block probably has 4-bolt main bearings.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!