SP2P 2bbl worth the effort?

The four barrel having, smaller primaries, will get superior mileage over the two barrel, especially the large pattern one. I like what what I have read about the Edelbrock StreetMaster and the Offy Dual-port, but SP2P was developed for motorhome usage and is probably going to make the most difference on mileage. Are you running an EGR? EGR would take a lot of tuning (Special distributor curve and lean cruise circuit) but I think it would yield the largest single gain. Is this your '87 and does it have 302 high swirl heads and roller lifters? Go with a Tri-Y header set to maximize your intake combination. There are some R/V specific cams that may be worth looking at to improve mileage too. Just read the rest of your posting, I imagine Rob is right, you are very close to all your going to get.