That valve looks fine but you're probably better with the 6-port jobby higher up as it not only selects the tank for drawing fuel from but also sends unused fuel back to the selected tank - otherwise (improbably but possibly) if you had two tanks, both brimmed with fuel (like for an expedition) and ran the tank that DOESN'T have a return line, the unused fuel would get sent back to the other tank, which is already brimmed, leading to dropping diesel on the road which is undesirable... that's why the pollack is so popular.
Unless - you plumb in some sort of short-cycle fuel system where unused fuel is tee'd back into the fuel supply line (my veg kit does something along these lines so that there's no return line at all to my Td5 tank.
As for the tank - only the 90 tank will fit the 90 - the 110 is a completely different design. the code for the tank is whk100040 which is the Td5 plastic 90 tank - but I beleive whk100060 is the same but intended for the american 90. Theres other plastic 90 tanks too for rear mounting as used in military wolf 90's but I don't know their codes.
You'll get one if you wait - I waited a month or so for one on ebay - but you could try the landy breakers in LRO.
or if all else fails theres always...
WHK100040 Fuel tank - 90 from XA159807 - Diesel
I couldn't find a picture of one, so cast yer eyes over mine part-installed - theres some black foam I fixed on which is bit confusing as to its shape, but it's broadly as deep up and down as it is wide front to back, if not deeper and with a big wedge missing from the nearside front for the exhaust to pass. The 110 one is much less deep and wider / flatter.
finally, as for the genuine parts Land Rover electrical switchover gear - it's not a simple kit as I'd thought - but 15 different items on parts catalogue page M77. No doubt costs a fortune! The "simple" mechanical system with levers etc is 34 SEPERATE ITEMS, and is on page J51.
Now I remember why I went for an electrical valve and 2 gauges / sender units!!!