I don't think it matters terribly much what you use. At this stage, all you're looking to do is get a bit of lubrication around all the moving parts. Some penetrating fluid is ideal for the bores if they have started to cling, but if not some clean engine oil would do. 20w50 is the recommended for a 2000, but anything similar would do for freeing off.
Your cylinder head looks nice and clean (although I don't think the 4-cylinder suffers with the same gungey/carbon-deposit issues as the V8). It also looks very dry (to be expected), so it'd be a wise idea to fill up the 4 square reservoirs under the camshaft. Your bucket tappets won't have moved in their guides for a very long time, so dumping some engine oil in the reservoirs will seep down and lubricate everything, as well as protecting the cam from scoring the dry bucket-tops.
What comes next depends on how involved you want to get. I'd be tempted to at least remove the head and sump to flush the oilways and replace the bottom end bearings, but if you just want to get it freed off for now and have a little fettle to see if you can get it running, it's pretty wise to start feeding the [by now bone dry] crankshaft bearings with a bit of oil.
The easiest way to do this without removing any substantial engine parts is to unbolt the external oil pipe which bolts directly up to the underside of the oil pump. There are two socket-headed bolts which are difficult to remove and don't seem to correspond to any Allen key I have. If you get it off, you can pour fresh engine oil directly down this pipe (so the oil goes into the engine block) while turning the crank over slowly. If you can't get it off, there is a (painfully slow) alternative way to do this. Just next to the oil filter is second external oil pipe, which bolts into an upright oblong channel (circled in picture). This is a priming reservoir for the oil pump. If you remove the two 7/16" bolts in the lid (taking care not to loose the O ring), you can fill up this reservoir with clean engine oil. There's no point filling it up till it trickles down the hole in the side back into the external hose - this will only fill the sump up verrrrry slowly and is a useless place for it to go. It needs to go down through the bottom of the square channel. When you're happy the engine is freed off, slowly rotate the crank by hand whilst maintaining the oil in this square channel (rotate clockwise from the front pulley, anti-clockwise from the flywheel). It will gradually disappear down the bottom as it gets drawn into the oil pump. After a long time (and at least a pint of oil) oil will have made its way to the bearings. The pressure output from the pump is negligible, so don't worry about spinning it faster - it's gravity or the capillary effect at best that will get the oil to the bearings. All you have to do is keep turning the oil pump rotors to prevent them obstructing the flow.
Either ways, once you've got a good pint or two in there, you can leave it for a bit and then come back a few days later to add a little bit more. If your engine has been standing that long, the bearings will be bone dry to the point of being porous. You need to get some oil to them so they can absorb it and become smooth and slippery again before you attempt to fire the engine up.
Keep us posted!
Michael