David,
You are new to this, so the overload of information you are requesting as a new boat enthausiast is a bit much. Many a boater jumps in and gets money invested in happiness, only to receive misery in the end. That is a recipe for selling, not enjoying this hobby.
Your first boat should be one you can go to the lake and have fun with, learn how to drive, and learn fine points like setup, prop selection, getting something you feel comfortable with.
Be able to join a club, and run with other boaters. There isn't a person on here that won't help you, but you are far away, and people you can run with will help your experience.
Hopefully there are races that you can attend, and that will be your most beneficial as a boater, other boaters running the same size boats, and you can learn a lot of the fine points of Tunnel boats.
Much of what we do ends up being defined by Dollar$, how fast do you want to go. Speed costs money. Fun is free, keep fun in it first, get settled in, then start to climb the money ladder. You will take steps up, and take steps back as you go into the modified engines.
Starting out your best bet right now is the OS XM 21 outboard. Reliable, parts are readily available, and run really good. I am running a 5 year old OS that gets bearings once a year, and still hauls butt.
You can upgrade this to a modified and will run well with minimum work, or you can buy a out of the box modified (CMB) and start the money game.
Run for a year enjoying the first one, keeping headaches low and fun high.
Start building the other one, and don't rush the build, you have a fun boat that will help you make decisions on the other.
And you have another persons opinion. Put a OS on your boat, start enjoying, filter through all of this and keep asking questions. The advice on here is great, but YOU are the one that has to enjoy it in order to stay in it.
I started over 20 years ago with a stock boat, got involved in a local club, and learned to have fun with other tunnel racers. I have watched many people jump in, spend unreal amounts of money trying to go "fast like him", and a year later you could buy all the stuff for 50 cents on the dollar......Fun first David.
Stay in touch.
Randy Premo