2000 XKR 55K Miles. I need guidance on what to drain or replace since car has been in storage with only fuel additive in 2.4 full tank. Battery Tender died and battery needs re-charge, and cam chain tensioner needs replacement. Should I drain tank and all related items ie fuel filters, fuel pump. or should FF, & FP be replaced?

Replacing all the fluids is a good idea based on the information you provided.

You should also post your enquiry in the X100 forum for XK8/XKR from 1999 to 2006. This is the X150 forum for XK/XKR from 2007 to 2015.

I'd sniff test the fuel and oil and go from there. Pointless to throw parts at it without knowing if it needs them. Expect the engine to run crappy until the old gas it out of it. Expect the filters to maybe clog if you have fungus growing in the tank. I'd rather slosh the old gas around the tank to absorb the sediment and carry it vs pump the tank and then use good gas to flush the sediment out.

I've fired up a lot of long dead engines without doing much until I know what they needed. Old school for decades dead engines was see if it would turn over , then pop the plugs and let the starter turn it over to check for spark, get some fuel up the carb and let the oil pump do it's thing. If everything checks out, plugs in and fire it off.

4 year old efi engine, charged battery and let fly.