RHS head to Magnum crate.
i have one of these...it is for 100% for sure a LA 360 block, with a set of magnum heads, as clearly stated on their website...i've liked mine so far as it dyno'd at 400 instead of the 375 base they give, and made 480 ft lbs over the 460 base....as far as blow by, i had a little too at first, but i've come to blame this on the cheap mexican made oil caps the cast aluminum valve covers it came with, i switched to PCV style breathers (plumbed to nothing) and it helped..may even run a breather can this year...but i've had several chrysler smallblocks behave the same way..and also never had a set of cast alum v covers seal perfectly....so imo, good motor, the quality issues you hear nightmares about were all addressed in the past. (a search for blueprint 408 on here may bring up some unfavorable reviews...but note that all the post dates are 2009 and back, after that they stop, and no news is good news!)
hanging new heads on this will require a new intake though, and the mag intake thats on it now retails for $300 i think, so be sure you resell that...you will also lose some of what i'd call "actual" lift/duration..b/c the mag heads have 1.6 rockers...LA heads use 1.5 in most cases...and the cam thats in these motors is pretty mild already...its in there for street ease..not the drag strip. .484 lift i believe goes to .516 with the 1.6's. just something to consider that you'll knock it back to .484 with la heads if u leave the cam.