Yes, you will definitely need it. As for what you can do for it, short of buying new manifold and exhaust, depends on how it has been welded. But you'll probably need new flanges (or, I suppose you could cut them off then re-weld them when you refit,) know anyone whose handy with metalworking and a welder?

You having any icing or stumbling probleams?

Running a stock exhaust?

I'll be ripping my old manifold off in about a month and you could have it for the cost of postage - but there's probably someone closer who has a spare stock manifold. For anything cooler than the outback you will need pre-heating for a single carb. If you run duals, or you'll never need to run at less than 25C ambient, youcan block the holes in the exhaust.

I just started to tear down a 1500, and its manifold had been repaired in the same area at least once. When I took the manifold off I found that the riser pipes had been blocked by placing a 2 cent piece at the junction to the exhaust (it fit perfectly). would this have been to stop air leaks or something because the repair job was a bit dodgy? What would happen if there was an air leak here?
It seemed to run alright when it was in the car, around the melbourne area, which can get a bit chilly at times, but then I never drove it that much.
I also am going to need a 1500 manifold if anyones got one.

Many people read (or heard) stuff about the pre-heater pipes reducing efficiency and blocked them off. If they didn't reduce their mixture and live in a warm enough climate to produce icing it didn't help. But we've all tried a few things that didn't help, then not got around to undoing them, haven't we? I drove a VW around Melbourne with that same modification and didn't seem to notice the problem - but I didn't know so much about mechanics then, and I don't know what damage it may have caused (the engine siezed from lack of oil and no pressure guage, and no part of it was rebuildable.)