You must keep any 1000 dollar investment!
A 4000 dollar Engine rebuild will ensure you don't wast 1000 bucks.
This is why some XE punters just grab old 4.0 XG/XH OHC's for 100 bucks, and then add a turbo, and go drag racing.
Before starting any thing, do compression test. If they are okay (160 psi, and no more tha 20 psi difference between cylinders), then do the static leakdown test for static leakdown.
This is an overnight pressure test at a mechanics shop, with his tools. If leakdown holds less than 80% of the test pressure at the end of the test, then don't go to modifications. Rebuild.
Once you've basically made sure the block and head are in good condition then you can look at the cost effective mods.
A correctly set-up Nitrous oxide is the best bang for the buck. Any BW auto will hate it. But a stock engine gace 130 odd hp, and it goes to 190 hp with Nitrous.
Extractors add 25 hp when a good EB XR6-style exhast with a bigger 63.5mm tail pipe is add. On XE sedans, its the only way to go until my dual exhast XE-XF kit hits the street.
Then go to a proper dyno tune.
For 1000, you won't be able to cam up a stock engine unless you the rest of the engine is in primo condition.
The cam and intake manifold need changing, and the best way of raising power with a carby engine is to fly cut the Webers 29 mm venturis out to 31 mm, then go for 7% bigger jets, and rework the intake manifold for more flow. An aftermarket Ultraflow intake is a very good item. The orginal Australian Design Rules (ADR 27C) need to be met on any 1982 to 1984 car. If the smog nazis don't catch you, an Edlebrock 4-bbl and Cain or Redline 4-bbl intake will make a big improvement. Check out the Aussie Forum, and see alloy daves 1967 XR Wagon with X-flow and all the drama. A great package.