Budget 318 build

Ok so my questions im gonna go with a double roller timing chain should i get the one that can advance or retard the cam on the gear is this gonna be necessary with this setup?
Yes, make the purchase. It may not be required. So why purchase it? Because you'll be happy that you have it if you need it rather than need it and not have it.
Should i just centerline the cam?
That would be just fine. Degree it or centerline it. Ether or, it is not a big deal on small cams. Degreeing it on big camas is super important. Also check valve to piston clearances with some clay.
What advice would you guys give?
There is a book called "How to rebuild my small block MoPar" that is a excellent step by step process with pictures book to own.
When your ready to step up the program, there is a "How to Hot Rod....." book which is good.
Ok next question i have a extra set of 360 heads will the stock 360 valve springs be any better than the stock 318 springs?
No, the stock springs should be turned into fishing weights, Christmas tree decorations, pen holders, biz card holders, projectiles for the brats next door or something completely else useless. Get the right springs for the cam.
Though I'd use the 360 heads on the 318 for sure!
The draw back is the extra head cc amount in the chamber. This lowers compression on a all ready low set up. While the flow will make more power than the compression, it would be awesome to have both. I don't so quickly recommend installing 360 valves into a 318 head due to cost and performance returns. But that and a full porting on a 318 head are an excellent combo. That is the old school way of doing things. But is very expensive with a low return vs purchasing a set of Edelbrock heads and ending up way a head of the game even with the extra expense of double checking the new heads at a machinists shop.