They sure do look close...
Capri:
12 gal. 37.77" x25.25" x8.5"
http://m.ebay.com/itm/231236967406?nav=SEARCH
323:
13 gal. 31.88"x25.75" x8.5"
http://m.ebay.com/itm/370728211004?nav=SEARCH
Weird the Capri has bigger listed demensions but the 323 holds more? I'm not sure I can rely heavily on these measurements. Does seem pretty close though.
That first ebay link I bought that tank since mine was rusted out. Shipping was great. I think I got it in 4 days, maybe 5. I've bought so many online parts lately I forgot!
They look the same which I thought until I got them side by side. There is one minor shape change which is no big deal at all. The bolt mount holes and hose connections are all exactly the same. The tank is well built and a worthy replacement. They include the pump assembly gasket and screws.
There was only one flaw but again no big deal. The factory tank has a little 2-3" strap crimped to on corner where you can mount the roll over vent to with one bolt hole. The replacement tank is missing that little mount. The rollover vent with two hoses and an electrical connection will freely hang right beside it. It doesn't fall and drag the ground or anything. I took a cable tie and secured it just to be sure. Just make sure it's upright so it doesn't think you flipped over.
Also the factory tank has three strips of foam glued to the top which the new tank doesn't have. I'm not sure their purpose. Either it's to keep metal to metal noises down or it's a little spacer to keep your top hoses from being crushed. They aren't an 1/8th inch thick. I think they are more of a cushion. I forgot to transfer them over and had no issues. You would need something like 3M weatherstrip adhesive to make a permanent bond as the old ones just fell off to the ground. I blew through the return line with no problems so I didn't worry anymore.