Like RatRod68 said, the L18 footprint is just like any other old big block which means for a 67-72 4x4 the engine may need to be moved forward for firewall clearance. One saving grace on the L18 is the fact it does not have a distributor and the early L18’s with EGR valves at the rear of the engine can be removed like the later L18’s to save the firewall room. Without a dizzy or EGR valve the L18 might just fit in there with no mods if the valve cover and coil packs fit under the brake booster. Maybe you can be the first to let us know
. I get a lot of inquires on L18 swaps, but never really see any getting done. Lots of talk on the forums but no action
The L18 oil pan will interfere with the original engine cross member where an ORD HD engine crossmember would fix that. You can even use older big block exhaust manifolds/headers on the L18. If running A/C, I recommend using 2001/2002 G-van accessory brackets to move the A/C compressor up to the top to prevent the need to hack the frame like so many other L18 and small block LS swappers have crudely done.
Meatwagon83,
It is an easy swap and much easier than a LS swap IMHO with greater rewards in the end. You could potentially gain more MPG with a L18 over a 454 depending what 454 you have. There is no doubt about it that a L18 will double your fuel mileage from a carbureted 454. I went from a carb’d 454 HO to the L18 and went from 5/6 MPG to 11/12 MPG with gobs more torque and horsepower. The OD trans also helped with the MPG. If looking for MPG increase alone, I don’t think an L18 swap would really be the answer though. Outside of the L18 acquisition cost, you are still looking at $1500 - $2500 just for installation components (wiring harness, ECM tuning, new accessories, exhaust work, etc). A lot of people use old donor harness from the truck the engine came from, I don’t recommend that. A new harness is the best $700 you can throw at a late model engine swap.