Cam suggestions for 5.9 Magnum in Canyon/Road racer?

That is a nice torque curve on that Hughes cam, though. Another consideration is if you're converting from a magnum front drive to an LA front cover. If not, you'll need a Hughes bolt and washer kit if you use an LA cam.
https://www.hughesengines.com/Index/products.php?search=7011&partid=11253
If you switch to an LA cover, you can use an LA hydraulic roller cam or core. I've done 360 LA in a 318 5.2 magnum once and the extra lift with the magnum rocker arms made an incredible grunt torque truck engine. We used early 318 truck manifolds and a chinese air gap intake with an Edelbrock 600. If you need an LA hydraulic roller core, post up a wanted thread here in a separate listing. One thing to consider with the Multiport EFI, though, is that they usually work better and are more forgiving on the tune with a 112 or wider LSA. I do recommend the 2.74:1 1st and 1.55:1 second gear set from an a999, A500 RH42/RE42 transmission and a custom converter. If you can go with that, Oregon Grind #1236 looks good from here. 224/[email protected], 274/[email protected], .554/.563 lift (with Magnum 1.6:1 rockers) on a 112 LSA. Almost identical to that Hughes grind in the dyno article. One question on the Edelbrock Multi Port; Is that the Pro Flo 4 EFI with the super victor intake? I would stay with a single plane for that system, but would be considering having an Edelbrock Torker2, Weiand Xcellerator, or Holley street dominator modified for the EFI rails. Edelbrock lists that manifold for a usable power range of 3500-8500, even in injected form. That may shift downward some with the fuel inlet point moved to the intake port flange, but that's still a lot of volume for something you want torque right now with. A 4150 style injector on an air gap manifold may be a better option.
Super Victor EFI Intake Manifold for Small-Block Chrysler LA Series Engines