Need your help choosing a Mossberg 500 to fit a Bullpup Unlimited kit

Hello, calling upon everyone's expertise here.



I'm looking to get a Bullpup Unlimited conversion kit:

http://ift.tt/1iy1kCB ...of an upcoming version designed for the Mossberg 500 platform: http://ift.tt/1BFilW0



I don't own a Mossy yet but given everything going on these days, want to pick one up ASAP. However, as part of the FLEX system, there are several versions of the 500 Special Purpose available:

http://ift.tt/1s3bL4P

...and I'm not sure which one(s) would be the best choice for the Bullpup Unlimited kit. Here's a few of the 500's models:

1. #54300 Mossberg 500 Persuader


2. #54301, Mossberg 500 20 Gauge, 8-Shot/adjustable stock/pistol grip


3. #50145, 500 20 Gauge, 6-Shot, 18.5" Stand-Off Barrel


4. #50450, 500 Cruiser, 20 Gauge, 6-Shot, 18.5" Barrel


5. #50452, 500 20 Gauge, 6-Shot, 18.5" Barrel

So the main requirements for any 500 gun to fit the Bullpup kit are that it can't have:

*3 ½ inch receiver

*vented rib barrel

*bayonet lug

*ghost ring sight



With me so far? Ok, thanks. Well the other main considerations are that I'd prefer to have 8 shots instead of 6. And for the barrel to be as short as possible- in the pics on the BullPup site, they have 2 different configurations: http://ift.tt/1BFilW2 & would only want the short one. (top pic)



Where I start to really get confused is how on Mossberg's site, each of the various 500 models has the same options (6 or 8 shot, 28"-39" length, 18.5"-20" barrel, etc.) selectable.



And just to make me even more uncertain, when I read a review of the 500, it mentioned a "ported vent-rib barrel with dual beads;" http://ift.tt/1s3bMFX ..which would mean it wouldn't work with the conversion kit.



Soooo...winding this down, very much looking for some guidance. Thank you.

Need your help choosing a Mossberg 500 to fit a Bullpup Unlimited kit