My experiences with M II kits is that usually the rack ends up higher than the top of the crossmember. With a front mounted rack that presents a clearance issue for the dampers on our inlines, something the V type folks don't worry about with their short funny looking engines.
With a rear mounted rack the oil pan becomes the major interference point on any engine. Power racks often have a larger diameter than manual racks at least part way across from the driver's side and some are larger overall from end to end and hose locations add to the situation as they run over the top of the rack.
Total Cost Involved, Heigt's and almost all of the street rod M II kits are engineered to lower the vehicle so the drop of their crossmember is relatively shallow to tuck everthing up closer to the frame thereby lowering the car. If you can't poke around some already installed jobs to get measurements or references then call whichever manufacturer you will be buying from and be prepared to give them as much info as you can. Since you already have the engine in place a good place to start is to measure from the bottom of your balancer to the bottom of the frame rails, and from the bottom of the oil pan to the bottom of the frame rails. Also use the existing beam axle rubber bump stops on the frame as a reference point for front to back locations of the damper and possible interference points of the oil pan. All of the M II kit makers use the original bump stop mounting holes at some point in the installation instructions as a reference point.
