Forge World Models, and twin linked weapons...

Ok, I just rolled back into 40K and WHAM!!! These 5th ed rules are great but... What in the world, the changes are drastic for some squads I had built prior, Blood Angels I have to tone down the plasma pistols, in fact I am looking at an assault squad that's got the base coat on them, and they are packing too many plasma pistols...

Then there are the models like the Land Raider Prometheus I cracked open today and started the pre-assembly build to observe how the bits go just so... I imagine I can use the Prometheus' rule for reserve re-roll, but what about the dual twin linked heavy bolter sponsons?

I guess I'm confused since I lost my twin linked heavy bolter turrets on my Steel Legion Chimeras... How do I use those?

Or am I missing the rules all together and they are still ok to run?

Signed,

Lost as Last Years Easter Egg