I've been trying to layout a budget and schedule for my future MkIV project and figured there are three major purchases for the kit 1) the initial purchase from FFR, 2) the engine/transmission, and 3) paint.

How late into the build should I plan on buying the engine/transmission? Is it something that can wait a few months into the build or should I just expect to buy the engine/trans around the same time I buy the kit? Obviously given the magnitude of those two purchases I am hoping to spread them out as much as possible but understand the lack of these elements may delay and hold up other aspects of the build. For reference, I am hoping to maintain a 2-ish year build schedule (sans paint). Any thoughts?