Not as busy as you might think. I've been doing this for several years now and I make install kits for both the pushrod and OHC engines. Except for drilling 2 holes, 302 pushrods are a bolt in. Minor hole enlarging of the firewall at the brake booster mount is required for the mod motors. We did the engine install on the black car in about 2 hrs!! As for fit, except for front to back length, the engine compartments of a Merkur, nee Sierra, is wider than the Mustangs these engines came out of!! It takes the better part of 8 hours to install headers on a 4.6 in a Mustang. It's about 30-45 min same engine in an XR. And 315RWHP from a breakers yard engine is pretty good going. It cost the equivelent of about 400 quid. And it weighs 40lbs LESS the the 2.3 4cyl it replaces!! I have a Camaro/Firebird T56 in mine. 1800 RPM @ 80 MPH and 26mpg. Best my 2.3 ever gave was 23MPG. Soon to have an 8.8" Independent rear diff from a Cobra/Lincoln Mk8 with 4.10 gears and a new front Kmember with a new front suspension design. This will allow (all at once) the V8 swap, big brakes, front mount sway bar, new suspension with 1.5" height reduction built in. You're gonna LOVE your car! Cheers!