I've already searched and read what I could find and I'm a little confused. I'm Running an 89 Firebird Formula, 305 Hooker shorty headers into full 3" exhaust. LT1 cam is coming. I got a line on the following and need to know if this would be a good addition:
305/5.0 Vortec heads
Replaces casting numbers 12552520, 12557113, 12558059
Applications include: (but not limited too)
CHEVROLET 305 5.0L
CHEVROLET 1500 PICKUP 96-99 8-305 (5.0L)
CHEVROLET 2500 PICKUP 96-98 8-305 (5.0L)
CHEVROLET VAN 96-02 8-305 (5.0L)
GMC 1500 PICKUP 96-99 8-305 (5.0L)
GMC 2500 PICKUP 96-98 8-305 (5.0L)
GMC VAN 96-02 8-305 (5.0L)

1.94" stainless steel intake valve
1.50" stainless steel exhaust valve
Viton seals
Springs Single W/D 1.25" OD X 0.78 ID 108LB @ 1.70 closed / 281LB @ 1.25 open 1.13 C/BIND (set up for a max lift .520 cam) Valve spring pressure @ 1.750 installed height 105 lbs
Thicker decks for greater strength
CNC machined guides and seats
Superior port finishes for increased flow
3-angle valve finish
Machined integral guides
Hardened exhaust seats
Redesigned water flow for greater thermal conductivity

 

The only Vortec head castings I know of are 062 and 906. The others aren't as performance oriented IIRC.

http://www.superchevy.com/how-to/97458/#__federated=1

 

From what I gather they are the best PRODUCTION 305 heads out the box. Again out the box not ported. For the $ I don't know if they are a whole lot better than the 081 heads which came on the 305TPI engines or the old 416 HO heads but im sure someone here could tell you. Either way these heads and cam would make a lil 305 run very well for what it is. GM rated the L30 Vortec at 230HP and you will be adding a lot better cam to it. You could wind up in stock L98 territory but im sure its been done here and someone could chime in which knows better than me. Ive actually thought about this setup more than once. Good luck! 059 casting

 

I assume those are aftermarket 'replacement' 305 vortec heads which have smaller chambers vs the "350 vortec" heads that everyone uses and benchmarks in the "performance" magazines and forums - those say they've got 1.94/1.50" valves which were used on the vortec 350 heads - the one thing I didn't see is chamber size which is why you would run a 305 vortec head as it has a 58cc chamber vs the larger 64cc chambers.

If they flow as good and have a small chamber for the 305 then they would probably be a good upgrade over the stock heads that are on there now.

 

Thanks for the help. I can do the work its picking the parts that I have trouble with.

 

They are 58cc so the next question. Any cam recommendations?

 

I think your LT1 cam choice is a good pic if its a daily driver with the other parts you have. If this is intended as being a daily driver that's just a good runner and a little quick I would keep the motor simple, throw some lower gears in it. If it dose not have a limited slip than I would add one and if its an auto modify the transmission then start on the suspension.

 

The Vortec 305 Marine engines with the little "395" cam that is 196/206 @ .050 is 250 Net HP.and 310 lb/ft of torque. They use a port fuel injected intake that has ~8" long runners, a large open plenum and a vertical, forward placed 70mm throttle body.