How much horsepower should I expect?

Well as far as the headers go, I did find a link to a pair, but it says it wont fit with the 727 transmission?? It is also a column shift automatic.. Is there a different part number id need? ( What will the HP difference be in these vs. the shorty block huggers? )

http://cgi.ebay.com/ebaymotors/Doug...Q5fTruckQ5fPartsQ5fAccessories#ht_1361wt_1167