BotP, I chose to keep the deck of the block and the head casting as free of weakening plugs and holes as possible. So I carved an adaptor plate out of 1" thick high-grade cast iron and screwed it to the block with many smaller flat-head cap screws. I then bored the plate with 4" holes matching the cylinders, bored the block plate/block (screwed together) 4.060" and pressed in a sleeves for a 3.875" ID, also the original 153 bore. There was a solid copper gasket between the plate and the block. Water passages were carved through and about the underside of the plate.... And for my next trick, the valve gear. To get the push rods from the lifters to the rockers would require bent push rods or piercing the cylinder bores and pistons, i.e. no direct shot is possible. Eight 3/4" holes were drilled through the plate where the stock push rods would have most closely passed each other, the stock rocker push rod and the stock lifter push rod ends "intercepting" in the plate. The hole was drilled to bisect the angles of intersection in both tangential and radial directions thus "eliminating" the edge loading. The holes were press fit with bronze bushings with 1/2"ID in which "slave lifters" about 5/8" long rode between the ends of the upper and lower push rods. GM lifters bled oil into the push rods for upper end lubrication. I drilled the slaves to use this oil supply for themselves. The Fiero TBI intake had a vertical manifold / head surface; the DeSoto surface was about 25* from vertical so I cut a wedge shaped spacer to fit bewteen. The coolant return from the engine exited the head through this surface between cylinders 1-2 and 3-4 so I drilled through the intake plate, put in hose barbs and routed the hoses to the thermostat and radiator. Oh, let's not forget the swapping of lobe locations on the cam for two-pairs. The cam was re-ground with a 60's 389 Pontiac HP profile. Oil return was via external tapping of the standard corner of the head passages via hoses into the pan. The system was augmented by routing the crankcase ventilation through the engine to pull the oil down to the pan. I ran this combo for two years and 20,000+ milea in Denver, -20F to 100+F. No major system or design problems. Let me know what you think. KalKlein
