Most effective was to replace the 360 in a 68 F0rd 3/4 ton flatbed with a 69 Lincoln 460. Same 9 MPG in town, but could pull my gooseneck stock trailer with six horses at seventy over the grapevine at about 3 MPG. Had 10 1/2 : 1 compression, but only needed to switch to the premium tank for hills.
Four carb Corvair in VW camper pulling race car could pass anthing except a transmission shop.
283 with iron powerglide in bugeyed Sprite used in slaloms.
Built 215 Buick in Alpha Romeo roadster.
252 Buick V6 with five speed, eight inch f--d in MGTD.