LA heads on Magnum block?

I know this has been asked/discussed before, but how do I use LA heads on a Magnum block? I searched the archives, but either it doesn't work right or I'm stupid. I read about oil-thru pushrods and oil-thru rockers, but nobody ever mentions a manufacturer/part number for those rockers. Also, can I use an LA cam and lifters in the roller Magnum block? See, I already have all these nice LA parts, but am only finding rebuilt Magnum short blocks for sale. Thanks.
My 360 magnum has a LA comp 550 solid lift cam in it with Howard's EDM oil through lifters