One thing nobody else said: You may be able to sleeve your 206 bores and then re-use the old pistons and rods.
I don't know what it cost now, but I am thinking the last time (2003?) it was $48 for the first cylinder and $35 for all the others.
The last time I bought pistons for a 206 they were $125 each.
Last thing: I put a 445 carburtor on my 302 and it seemed to work with no problems I never worked it hard. The correct carburetor has a right much larger bore in it, however.