I had the Piper 285 in a built up 4.6... big valve/ported heads, higher compression, etc.
It was definitely too much cam. Great power on the road, (really great) but I could never get it to idle right. It wasnt just lopey, it was mullet/camaro fire breathing lopey.
So my suggestion is, something less than a Piper 285. (or paint a trans am bird on the hood and go for it)