help with 340 hp manifolds and TTI 2.5 exhaust

Just my .02 TTI 2.5 exhaust is meant for headers I think? I went through a Torque tech exhaust mounted to Headman headers 20 years ago. I had to make the "headpipe" or the part that bolts to the header collected flange. I had to cut an angle on the pipe and weld the flange on. This was to get the 2.5 pipes "close" to the pipe cutouts in the frame near the trans cross member. I have now decided to go stock style exhaust from accurate exhaust. Anyway point is, you may have to make your own headpipe. As in fit the head pipe to the manifold with a loose flange, and tack weld, then remove and finish weld on the bench I see the pic TTI sent has headers in it. I dunno, another option would be to mod the x pipe? Either way welding i think.