DUDE! I've been reading your posts along this line for the last two weeks now (at least), and it's really starting to sound like you just want someone to tell you EXACTLY what to do with that engine. But we can't - all we can do is give you advice, and you've gotten more advice here about this subject than anyone I've ever seen. You just keep posting the same questions with a slightly different spin.
Sorry for ragging you, but at some point you're just gonna have to quit worrying about whatever it is you're going to do, and just make up your mind and do
SOMETHING - otherwise, you'll never do anything.
Let me break it down for you into the simplest form - you can do one of three things. 1) not rebuild that engine, and just add your top-end parts; 2) pull the engine and do a complete rebuild before adding all your top-end parts; 3) buy a short block, then add all your top-end parts.
First thing to consider is projected engine life. You're in the process of doing some major work to that engine right now, and you don't want to have to do more once you're finished with this project. The engine has 165K miles on it, so it could be good for another 50K or so. Or it could die at 180,000 - you don't know, and you really have no way of knowing. So my suggestion is, since you're going as far as you are with the top end parts, don't even consider not doing something about the bottom end. That leaves you with choice 2 or 3.
So, next comes the tougher part. Rebuild or buy a short block. There's a whole host of factors that could play into this decision (time, money, ease, right tools, what you want from the engine, what you might or might not do to the engine in the future, etc). Bottom line is, if you have the money and would rather not mess with rebuilding the engine (for any number of reasons) then buy a short block. On the other hand, if you have all the right tools and want to save as much as you can, pull it, disassemble it, take it to the machine shop and then do the rebuild yourself. This has the advantage of not only knowing you have a fresh engine that you're not worried about, but you'll have the experience of doing the work yourself and learning that engine from oil pan to air filter.
If you want my opinion, rebuild it. And just go for it and do it yourself. The first time I rebuilt an engine I was a little worried about it, but it wasn't hard in the end, and it was a learning experience I value to this day. And I got through it in the days before Stangnet (before the internet at all, actually) so with Stangnet as a resource you're sure to have very little trouble. So don't let that stop you.
But whatever you do, just set a time frame for yourself, make a decision, and go with it. If you don't make a decision, you'll never get anything done about it.
That's about all I have to say.
Matt