If it's the factory drivetrain from a '79, that would NOT be a T18. It would be an NP435. Not that it really matters, they're real similar.
I have a NP435 in mine and the hydraulic clutch works fine. I used a Speedway push style slave cylinder and the factory master cylinder. Bracket was just a piece of angle iron with holes drilled in it, although it bolts onto a hydraulic clutch style small block bell housing. Your 351M bellhousing wouldn't have a provision for that so you'd have to mount the slave cylinder somewhere else.
Ideally for you, I think the 351M is a total waste of time. They are big, heavy, gas sucking, inefficient turds that were designed during the worst of the smog years. But if it's all ya got and gas mileage is not an issue at all, go for it, it's better than some alternatives.