get right to the point

i have a cut downpipe because the person before me had a custom exhaust so now i need to get whatever test pipe of whatever welded on.

now can i just get 3 inch exhaust tubing and weld it to the down then weld it to whatever exhaust i get?

 

Yes technically you can do that...although the point of bolting it together is so that you can get it apart if/when you need to remove it. If you weld it together and need to remove it for any reason you're going to be dropping all the hangers, and unbolting the headers to drop the exhaust. Make it easy on yourself and get some flanges welded on where they normally would be so you can unbolt everything...I'd wait till you get your aftermarket exhaust and have a downpipe and everything fabbed up to bolt to the new exhuast.