Thanks for all the feedback, guys. If I choose to let my engine builder proceed with the 64mm throttle body (instead of something smaller like most of you suggest), what will I notice when riding? Too jumpy on the throttle response? Poor fuel efficiency? Just asking because I have no idea what to expect.
It sounds like this HD tech believes you want maximum
horsepower, since you asked him for a significant increase in
power. That would be fine if you were going to run only at the track at high RPM.
Check this:
Do not be shocked if a guy on a 110 with a cam can pull away from you with ease.. That kit would need to see a high rpm number to be making any real tq.
For street riding, you need a build that develops
torque at lower RPM. Here's a suggestion: Post a question asking for recommendations on a good builder; and, just as important, determine what you want from this bike. Do you want something that is only usable at the track (all high RPM running)
or do you want a bike that hauls a$$ from a stop
and has plenty on tap for passing from 40 mph to 80 mph? The people on this site know the difference between the two types of build, and the advice you've gotten here is right on target.
As for your question about the 64 mm TB, look at this another way: Why would you
want to go with the 64? What are you going to gain with it, that you can't get with a smaller one, other than bragging rights? And how will you feel when far cheaper builds leave you in the dust?
This HD tech and this build are just setting you up to spend big money---once for this build, and again when you take it somewhere to make it right. The advice here will save you money and the hassle of a poor running bike that has to go into the shop to be rebuilt.