With 2K to spend and the fact that you already have those parts I would suggest a cam, some headwork and a compression increase, re-graphed distributor, a well matched exhaust and some time on a dyno to get the whole shooting match tuned to perfection. Is there any way to can increase your budget as getting 100hp/litre reliably will probably cost you more than $2000 IMHO? Little things like electronic ignition and a beefier clutch will make the car alot nicer for example.

Regards Matty