The later Iron Duke head can be made to work. If I remember correctly, you have to relocate one head bolt hole in the block. I was already too far along with my old siamesed port head to change directions. (Maybe I'll do another one with the engine I'm pulling out and use a Pontiac Super Duty head and manifolds!).
Those later roller camshafts also have a second distributor drive gear.
The standard Iron Duke block is thinner cast and the cylinders are shorter in length, so using the 181 crankshaft requires an extra long connecting rod to keep from pulling the piston out the bottom of the cylinder. Same is true of the Pontiac SD block!! Again, without going back into my notes, it takes about a 6.250" rod to make this work and those would be special order if available at all!!
My research says the standard Iron Duke block is deficient in strength in several areas and the stock crankshafts are JUNK!! They also lack the motor mount bosses to allow easy installation in a longitudinal configuration.
Don't forget!! The inliner Chevy rod is DIFFERENT from those of the SBC!!
There is some extremely good info over on the FIERO forum! There's a guy over there that has played with several combinations of the "Duke" and combining parts from the Chevy II, the early Iron Duke, the Mercruiser 153/181, and the industrial 3.0 GM engines!
