Have you priced exhaust system work lately?
Dont, itll scare you...

The intermediate pipes (manifold down) can be bought, or made relatively easily.

Since the Y pipe apparently isnt available, I made a dual system, works great.

The drivers side is just about a 30 inch, 2-1/4 pipe bent at 45 degrees at 15-1/2 inches from the donut flare ( spherical flare) , then that leaves a " straight pipe" segment pointing back. It runs below the frame member to keep away from the transmission. That would cost some ground clearance but this truck is street only and the pipe has never hit the pavement.

The passenger sides not so easy, a simple 45 bend didnt fit well especially with the O2 sensor. The correct pipe comes down about 7 inches then does an S bend about 2 inches to run along the inside of the frame, and then needs a 45. Oreilly had an old 1980s- 90s S 10 Walker pipe that worked with some shortening then into a separate 45 elbow. An O2 sensor bung must be welded in so its not just a simple clamp job.

OReilly has a large selection of Walker and other parts. The Walker pipe for old S models cones in 3 lengths, they only had the longest one in stock. They were noted as fitting the 80- early 90s S -models but obviously before the O2 sensor era as there was no sensor bung in the pipe. Youll have to hunt for the parts, these auto parts generally have youg kids working there that have no idea how to find such things.

The exhaust manifold " donut" gasket needs a steel insert to prevent the hot gasses from eroding the gasket, it should come with the gasket.

BTW I made the entire system using a box of pipe bends to fit, had a shop make 12 inch pipe sections bent every 5 degrees, and fit, marked and tack welded them into strait pipe sections. Not quite as clean as original, but its worked for15 years +.

Note: dont do what I did- put header wrap around the down pipes to try and keep the floor cool, the water destroyed the pipes. That might work with stainless pipes...