Just need a budget for now. Are you doing the work yourself? Whats the LS1 spec?

So what is an exhaust, air filter and remap likely to equate to? I.e., what's my ls1 with wortec sport pack really making?

The tune is the most important bit as there is likely some left on the table to start with. If I were on a tight budget, I'd be scrounging someones cast off 253 (LS2/6) heads cheap, find an LS6 inlet (if your doesn't have one), a take off LS2/6 cam off someone (or get a set of 1.8 roller rockers), I'd be going mafless, working the TB and filter box. Try and get a used set of headers and up the exhaust size. You should make around 350ish at the wheels set up right as I think ringram has with an LS1.If the money is there, new cam and springs (£500 ish?) to get you nearer 400.

My camaro has pretty much exactly what Gareth just listed.
It dyno'd stock at 298rwhp just with a basic tune through the auto.

Its now got headers, intake, manifold, cam, heads etc. Not sure what to expect now. But 350-370 would be good. The idea was a budget build. Cam is a girly 219/227-112 but with over 0.600 lift..

On an ultra tight budget I think 370rwhp is doable. LS6 intake, small cam and 243 or equiv heads. That exhaust isnt ideal. Probably ok for 370rwhp but you will leave some on the table after that.

243 heads are a good idea. The 99 has the crap ls1 intake just swapping for an ls6 intake is worth 20rwhp so basically essential. Check with MF or another vendor for an intake.

As Gareth says probably half your gains will come from the tune.

Waiting for a replacement trans as the stock one doesn't like the new stall or power.
It goes sideways on demand as it is so no useless FI required

Excellent news !

What sort of exhaust, filter and map though. And what's the starting engine?

ls1 heads 230cfm
ls2/243 heads 260cfm
cnc ls2 heads can be around 310cfm

In theory my cnc ls1 heads (via Stevie, thanks!) were rated at 296cfm

Then it goes up from there, AllPro 12-2 heads flow 435cfm but you need a 0.750 cam to get there plus a 4.125 bore etc..
Forget them unless you want insane power and an equally insane bill. But 900bhp NA is within your grasp

AFR heads are good as are MAST, WCCH, TFS etc.

Dont just buy heads based on cfm! Look at port cc and cross sectional area. What you want is an efficient port.
Also look at where it tips over if the port backs up on the flow bench it will back up on the road much easier.

Compression is also your friend and dont forget valve lift. Its free power. You just need to pay attention to valvetrain.

TFS do some 220cc "as cast" heads, which flow really well and cost bugger all. On a budget they would be my choice unless you can get some cheap cnc 243s somewhere.

For max effort LS1 Id look at AFR 205's or their new 210's forget anything that looks remotely like a MAF, if you put it anywhere near your engine your project will fail instantly.

I like Simon's 223/231-112 cam. Its probably as large as Id want to go on an LS1 for a daily drive with traffic action. Of course an auto and stall will eat any sized cam.