You want a small cfm carb on a 260 if not going Qjet, think Holley 390 or Edelbrock 500. The SP2P is a very low profile intake, idle to 4500 rpm with small triangle shaped intake ports. You will gain a very small amount up top regardless, I would add a square to spreadbore adapter. There is a ton of room to add adapters, the intake is lower than stock. Even that thin gold plate should wirk. When I had the SO2P intake on an Olds 307 then a mild Olds 350 in my 78 1/2 ton. Part throttle was great, like EFI. The top end sucked, it fell on it's face, too much carb with the Qjet, the air door would need adjustment for less air. I had it on my 94 4x4 with factory TBI on the Olds 350, it worked very well, I should have left it there. I thought it was limiting top end with the maybe 500 cfm TBI but it was throttle cable issues, fine once fixed but I went A4 anyways to match the 307 heads. I would think 500 cfm would max is what that intake or the 260 heads could take. Either the Holley or Edelbrock carb should be purchased with a tuning kit, probably way rich out of box. The forced air, dual exhaust Olds 260/TH2004R/3.42 combo is one to consider. Peppy and very good mileage in town or on the highway, 26 mpg Imperial highway, shooting for 30 mpg in good weather, town is similar. I gained 5 mpg highway over a 260/TH350/2.78 combo. If you kill the 260's mileage, what the hell is the point of the 260?
)
