The Verlinden set for the (A)1 is rarer than the proverbial hen's teeth. I've been collecting bits for an (A)1 and an (A)4 for a couple of years and I've never seen one.
If you can still get hold of them, I suggest these books.
Project LVT's: Amtanks, vol 1 by David E Harper. Published by Letterman Publications, modelmecca.com. Vol 1 covers the "Amtanks", vol 2 covers the LVT2 and (A)2. These are modelling build books, although using the old Trakz conversions. Some useful real vehicle photos, but not a lot on interiors.
Letterman also published a separate set of exterior line drawings for these vehicles. I got copies of both books and the plans on eBay.
The Osprey New Vanguard book on USMC Amtracs isn't much use. Lots of history but not modelling-oriented.
Squadron-Signal do at least one "In Action" book on LVT's. I don't have a copy. so I can't comment on its usefulness. It is definitely still available.
I know the (A)1 turret was not identical to the M5 turret, but it was very very similar. How different would an M5 interior be, accepting no co-ax MG and ammo stowage?