Replace 170 with 225

There is no difference in the manifolds. Grumpus is correct about the oil pan and pickup, but not about the dipstick and tube. The existing exhaust headpipe may hit the floor when you lift it the extra inch to meet the exhaust manifold outlet (the 225 block is an inch taller); you can put in a spacer or have a new headpipe made. If you are installing a '68-up engine in front of a '67 or earlier automatic, you need the 1/8" spacer ring to go between the early small-nose torque converter and the late large-bore crank flange or else you'll lose trans front pump bushings and seals.