OK i am thinking about ordering a f13 cam in the next few months here. My question is futural motor sports has 2 upgrade packages with dual valvesprings.
1. Futral Motorsports Cam Package Upgrade - Add Manley Dual Drop In Springs, Manley Titanium Retainers, Manley Seats, Intake/Exhaust Valve Stem Seals, FMS Hardened Pushrods to FMS Cam Selection (This is an upgrade only when purchasing a camshaft)
2. Futral Motorsports Cam Package Upgrade-Add Precision Race Components Dual Valve Spring Kit (Includes dual springs rated to .650 lift, titanium retainers, seats, intake & exhaust seals), FMS 7.400" Chromemoly Pushrods to FMS Cam Selection

Can these upgrades be added to a bare casting Dart 225 set of heads?
I'm just learning all of this, so please forgive the rookie question. If anybody can explain the difference between single and dual valvespring upgrades, besides the obvious(single and double,duh?), that would be awesome.

One more quick question btw. Would a set of Harland Sharp 1.7 rockers be a good addition to this. At least better than stock rockers and worth the $400? Thanks!
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the dart heads will come with springs suitable for your cam choice. not much advantage to upgrading. and bare casting means you'll need to put valves in the head i think. just buy them assembled and be done with it. bare casting is for people who want to do some home porting.

the pushrods are a good upgrade, but you should be able to purchase those separate.

the stock rockers are pretty good. there really isn't much need to upgrade. you will see minimal power gains if any. only reason i have them is cause i got them as a steal...brand new in the box, less than 1/2 price.