100 extra CCs and a couple different gear ratios, or maybe just 5th. I would prefer a Venture block for my Vmax just to get that more cruise friendly 5th gear. I would probably use the Venture final drive as well because I do so much open road. I own and ride an 89 1300 Venture and I feel like the gears are perfect for the V4 if there is a decent % of highway use but I find the stock Vmax gearing leave it feeling high strung on the open road, I'm always looking for a 6th gear.
I researched it at one time and I believe the extra 100cc could get you an extra 10hp or so at the crank with no other changes (with the Vmax top end). Sean may know more specifics, I think he has some experience with Vmax headed Ventures blocks.
I have a set of Vmax heads/cams/intakes that I am/was planning to put on my Venture.