There is a lot of good info on the jet boat performance web site. I can tell you from my past experience it takes a lot of $$$$ to make one go fast. The speed is definitely in the pump. I was very lucky to have one of the best boat builders in the country by the name of Jim Youngblood guiding me in the right direction   ( Google his name and you will see what I'm talking about )   You can put all the motor you want in a boat but if the pump doesn't have the correct impeller it will be all show and no go. As far as the huge rooster tails you get that from a jetavator  as far as a performance helper it isn't it just directs the water from the pump into the air.  My opinion a big block is the way to go  can't remember but for some reason the cams with a 112 duration works really good in those motors    I had a boat similar to the picture you posted that had a 500 cubic inch big block Chevy  a Berkeley jg pump with a b impeller the best speed I ever got on gps was 68   In order to get the 90 to 100 mph that I wanted  I was about to build a 572 bbc and go to a dominator pump in which was going to be a huge expense   I will tell you this they are a lot of maintenance   I now have a pickle fork hull with a outboard. You can take it to the lake. Hit the key  run a 80 mph for a whole lot less $$$ and work  I know the jets are great sounding and fun  but a outboard is a lot user friendlier