I have a pre-ban rec'ver kicking around and I was thinking about changing it to an upper that I can use. Think this is more trouble than it is worth and I should just sell it?

I would think I would only have to shave off the bayo lug and weld on an ATF approved muzzle break, correct?

I presume you mean that you have a preban LOWER receiver "kicking around".  

If so, why not just leave the whole rifle in a preban configuration which only involves the upper receiver so long as the rifle has a fixed stock attached to the LOWER receiver.  It's worth alot more as a preban so long as the S/N is verifiable as a preban.

If you really want a postban upper configuration rifle then just install a postban upper.

I have a pre-ban lower and TWO pre-ban UPPERS. I was thinking about converting the 20in into POST-BAN since I never use it...I am not going to buy another overpriced pre-ban rec'ver.

That's basically what I did here:

ar15.com/forums/topic.html?b=1&f=74&t=154400&w=searchPop

Yep, shave the bayonet lug and have the flash surpressor pinned or silver soldered.

Cool....just wanted to get some input! Thanks!

I'll post some before/after pics if I go thru w/ it instead of selling the upper.

I did one of these for myself a few years ago as a "why not" project and have since bought the tools and done some for friends. Just shave the lug, and have a gunsmith cut off the f/s threads and recrown the barrel(with a couple of basic tools from Brownells you can do it yourself). This becomes a low cost post-ban upper that shoots great (yes, I've read the posts that say you can't cut a chrome lined barrel, but I've never had a problem with one shooting well after being cut and crowned).

Can't have a flash suppressor, even if it's permanently installed.  He'd have to remove the suppressor and permanently install a non-flash suppressing muzzle brake, or have the threads removed or permanently covered with a muzzle nut.