188 and 201 are the same bacic blocks and require the same Major work to install !
These blocks are Longer and will alter wheelbase and share no parts with the VAC block, The early 148 and the VAC 124 share most major parts like Head etc and Bolt on from one block to another!
On the Red side the Combine/power unit blocks are the same as a IH 444 and started life as a farmall A type block was inproved and made larger as years went buy until it went from a 113cid up to a 153cid and shares most major parts and is like putting a 148cid in a VAC !
I Have Both Brands and Putting a 188/201 in a VAC is like Putting a 350 Farmall engine in a C only smaller (175 cid) and they would Gripe about that also!
Cliff S