I called GW Mail Order ...

[Shadow Queen]

The other day and asked them if they will update the Razorback kit and bring it in line with the 5th edition codex,

thier responce was probably not, as it would take time.

I said I have 3 Razorbacks that are awaiting 3 Assault cannons.

the responce I got was get the redeamer upgrade.

thats ok if you have money to throw around unlike me.

[Rapture]

I know they aren't the same as the actual assault cannon from the LRR, but the ravenwing sprue comes with 2 assault cannons that you could try using.

[gwensdad]

I used the ravenwing assault canons and with a little bit of modeling it looks alright on my razorback. (and has credit for 2 Eldar tank kills)

I may upload something to the gallery later.

[The AKH]

You don't actually have to buy a whole LRR to get the assault cannons - the sprue with the assault cannon turret and the crusader/redeemer sponsons is available to order separately.

[gwensdad]

Can't get a great picture, so I put the crappy ones in my personal gallery. (um, how does one link to a personal gallery anyway? I also put the keyword "Razorback" if that makes it easier to find)