Concerns- An engine that revs to 6500 with power isn't exactly what I call a reliable cruiser. It will need a little more messing with than normal and the bottom end/midrange (where we do most of our driving) will be a little "soft" to 3,000rpm (or so). I've run an engine like this on the street, and while it's a lot of fun off the stoplight, if I was building an engine that size for someone that wants more power but is looking for reliability as well I'd use a C35 or W110 (with 1.25 rockers) so it would only go to 5800 or 6,000rpm with power. This would provide more power through the bottom end/midrange and get better mileage as well.
The bottom line- While this engine will beat Jim's, it's not the jump in and go anywhere, any time powerplant that I think you are looking for. The normal rpm range of an Engle W120 is about 6,000rpm, while the C45's range is 6500 or a little more. The difference in duration is 8 or 9'- the W120 has 253' dur @.050" while the C45 has (I believe) 262' @ .050".