Drilling a Magnum intake for '73 'J' heads?

Ultimately I'd love to find a gently used (yeah, right) M1 as Prof Fate & Mr Porter have illustrated but I'll keep the Holley in mind if I run across a nice one. I'm a little leary of some of the clapped out examples on the Bag.
As others have correctly asserted, sell that beauty to somebody using Magnum/Magnum based/patterned heads, & use the coin to buy the correct one for Your project. What You need is floating around out there, patience & eyes peeled, You'll get what You want,....peace!
Jim K6