How is the best way to mount a Hakko Bed 24 sight and an arms 40 sight on an ar15/M4 flat top? Would it be better to buy railed hand guards, or mount a top rail on the standard carb hand guard and would it be flushed with the flat top receiver so when Bed 24 extends beyond flat top receiver.

I've got a BED24, and it won't fit on the flat-top with anything EXCEPT the ARMS#40, and even then you can't use the "multi-reticle" feature because the #40 won't let the rear lever move to the two middle positions.

I purchased a Daniel Defense 9.0 forend for my mid-length.  I put the front clamp of the BED24 on the forend rail, the rear clamp on the receiver, and it works with any BUIS now.

I wouldn't get an extension because the BED24 is already so tall that the iron sights sit in the bottom of the window.  Any higher and you couldn't see your irons at all.

If you don't already own the BED24, I'd look at OKO first.  It's shorter, so it fits without a forend, and I personally think the OKO I had was clearer than the Hakko I have now.  The Hakko is good, but I think the OKO was better.  YMMV

If you DO already own the BED24, then I'd personally suggest taking a look at the YHM forends, as they're good quality at a good price.  Daniel Defense is higher quality, but at 3x the price.

does anyone else have more to give me on this issue

The reticle selector is easily modified to use with a BUIS. The newer BED35 is much shorter and has an improved mount. With it, you'll have no "real estate" issues. I'm not an OKO fan. The Hakko is a much nicer sight, IMHO.

Thanks for your input I am here to learn for you people that knows, I have carried, fired, slept, and fought with the m16, m16a1 and finished off with the m16A2 and a 9mm with just steel sight this is all new to me. thanks again.

How would I Modified it

The mods I've seen (and done) are to dremel the reticle selector tap to clear the BUIS. With a #40 you'll end up cutting  the tab off and using strips of skateboard tape on the sides of the selector to turn it. Touch up with Birchwood Casey Aluminum Black. The KAC 300 Meter sight is easier to clear. The tab can be beveled on the bottom to clear and still have a tab for switching reticles.

Could I use a ARMS 38ex sight and rail and would it fit over my M4 handguard

Quoted: Could I use a ARMS 38ex sight and rail and would it fit over my M4 handguard

Not sure about the handgaurd clearance. The Hakko might seem a little high on a raised rail as it was designed to be the right height for a flatop reciever. Sorry I can't be a little more definative. Anyone else?