Cam help

If you want to keep the stock converter, you'd probably do well to keep the advertised duration down to about 270-274, and with stock magnum heads you'll need to keep the lift no higher than about 510" or so...any more than that and you'll start touching the retainers to the guides.

With your roller blank, you could call up either Bullet cams or Oregon and have then regrind the stock cam for a little bump in both duration and lift...they can also tighten up the LSA a couple degrees if you want. And yes, you called it correctly if you want to retain a pump eccentric, the 88-91 LA core would be your better alternative compared to the Hughes snout extender...