Pops,
No the F head won't bolt up without problems. There are a couple of stud holes that the F head doesn't use for oil drain back that the stock K head does. Bolt up the F head and you'll be drenching your cylinder block in oil! The fix is relatively easy. Set down the K and F heads side by side and you'll quickly see the two head bolt passages on the F head that aren't solid metal. Take the head to your local machinist and have two sleeves inserted into your enlarged holes to bring the head bolt passages back down to the stock diameter. A little shrink fit for the sleeves and it now bolts on without problem.
Build the motor big if you're using the F head. Yes, it flows more air than the K head, but for smaller motors it will perform worse unless you get a really good head porter to epoxy down the intake passages to improve partial throttle air velocity.
I started with a 73mm big block when I added a F head. Went with a 900F crank (+ 6mm stroke) and had head very well ported by a major east coast bike head porter. With my custom torque converter I launch at 6 grand and have peak horsepower by 7,500 rpm with a one horse loss by 10,500 rpm. Very flat powerband is what all drag hondamatics love. I can run high 10's at 124 mph in it's current state. There's more there - the crank can be rewelded and stroked more. I haven't brushed the cases with the aftermarket steel rods that I run. There's an easy 2-3 mm more there that will improve the midrange more. I'm probably a little under carb'd. I probably should go to 36mm CV's on it. Any of the above items will help, but it's major work.
When you get to making 100+ wheel horsepower, the stock clutch packs need a little help. I went with narrower steels and added one more friction plate. Rather than adding another ~5 horses, I'm looking more at the transmission for improvements. The 750A has wide thick gears in the tranny. Look at a current 600 cc transmission. You can fit twice the gears in the same space. My next major project will be trying to make a 4 speed automatic. That would be worth far more than 5 horses here or there would. I'd expect an easy 5 tenths minimum with two more gears.
Another thought - If you're going to do the work, do you really want the F head? Look at a 900F head to go with your 900F stroker crank on your Hondamatic. Yes it's more work, but it should yield more horses. Think of a base adapter plate made for the stroke increase and to allow a new head stud pattern. That head won't extend the rpm range much. That's the limit of that dohc head design.
Don't think that the new Honda will repeat as well as the old Hondamatics will. Shifting isn't the question. Launching is the question. I don't think that the current bike will be anywhere near as consistent in the 60' times. I'd love for someone else to buy one and do the testing. If it can be as consistent, I'd consider buying a used one. I'm not interested in yelling to the world that I race something different. Your dial-in board does the yelling for you. If I can run 10's, I'm ignored for the first few rounds. Anyone who gets near the final gets the once over by the competition as we both know.
Hope this helps or at least gives you some thoughts.
Jon Weeks
