A very good friend of mine is very interested in getting a Surly Long Haul Trucker (frame only) per my suggestion. He's looking at the 700c LHT frame. He currently has a Peugeot UO8 that he's had for 41 years with tons of great components that he's purchased over the years, including a major upgrade of the drivetrain earlier this year. Nevertheless, he's ready to move to a newer frame. He wants to get into more serious touring and French threading doesn't help.
To keep costs down, he wants to transfer as many components as he can to the new LHT frame. He knows that there will be inevitable things like a new bottom bracket and headset that he will need to buy. The main thing, however, is whether he will be able to fit his good quality 27" wheels/tires on a LHT frame and reuse his Mafac canti brakes. I can't remember if there is anything else he needs to pay attention to for a smooth transfer of components.
Thank you all for the help.