How are your existing heads? I "think" (or I arrived at this conclusion by using the process I use instead of thinking) that you can swap your heads and FI and spark onto the dohc block, with only maybe having to drill the new oil filter adapter mounting location and plugging the old one. IIRC, the motor mount may seal off the old location, but I'm a little paranoid about that. I'd tap and plug...

Not responsible for advice not taken...