I have a 1988 f250. The local guy at the exhaust shop (farmer john owned) said that he couldnt put dual pipes out the back because the rear gas tank was in the way. Is it possible to run an exhaust pipe in front of the rear tire? if so I was thinking just pipes on each side, right off the manifolds with no catalatic converter or mufflers or nothing. Tell me what to do with the 02 sensor and that. What will it sound like with a setup like that? how about performance? I dont want to spend the big money for good headers so thats not an option.

 

Forgot to mention. I want to put on an X-pipe. What size pipe would you use for the whole system

 

I have an '89 Centurion F-350 that I put dual pipes out past the rear axle then flared to exit just in front of the rear bumper. Since the truck has the 33 gal. Bronco tank on it there was no way to come straight out the back. I went with Doug Thorly Headers which are an excellent fit and smog legal but not a low dollar item($680,ouch!). They came with the o2 sensor hole pre installed so it was an easy install.
I experimented with several layouts as far as with and without muffler/cat. I actually found that a straight pipe off the stock cat, split prior to the axle and routed back to the rear bumper on either side, sounded the best. It gave better performance than my current setup of no cat and true dual pipes off the headers with 12" "glasspack" mufflers. Also had it set up with no cat and a Flowmaster Bigblock muffler, but I was not pleased with the sound. Straight pipes and no cat sounded cool for about 3 minutes and was then just plain obnoxious.
As far as pipe size, 3" all the way back to the axle, but had to neck down to 2.5" over the axle and then ran in to 4" tips.
Don't know if this will help any, but might give you a few options to consider.
Good Luck

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