Can you tell me if the aluminun cylinder heads from an 86 Corvette will work on my 84 Cross Fire and if so will I need to modify anything?
     
                Thanks  

Yes, the heads from your 86 will bolt onto your 84 cross-fire motor.  

Thanks Phil,is 86 the only year that will
work,have a line on several pair of heads,unsure of all the years involved.  

As long as the heads are NOT of the LT-1 variety, any year will work. The LT-1/LT-4 heads flow coolant differently.

Any year L98 head will swap over to your cross fire motor.  

L98 heads were on all standard Corvette's from 1985-1991, they are direct bolt-ons.  I would also recommend trying to get the fuel-injection manifold/intake for the L98 as well and not using the Cross-Fire.  Or switch to a carb manifold.

Also, GM's Vortec & Fast-Burn heads are also good upgrade choices, as well as any number of aftermarket heads from Edelbrock, Dart and the like.  

Sorry it took so long to reply to your message. Isn't it a big deal going from TBI to TPI or carb ? My other question is why go to aftermarket heads ? What is wrong with L 98s   Car has stock bottom end and a ported intake manifold .  

There's nothing wrong with the L98 heads, it's just that combustion chamber and port designs have improved since they were made. The weight savings alone replacing your cross-fire iron heads with aluminum will be beneficial.

For a budget performance head, the L98's not a bad had, with some mild porting work and a good three-angle valve job, they'll do just fine for your cross fire engine and what you want to do with the car.

For best results, you want to have the intake manifold/ports matched to the intake ports on the heads.  

Thanks Phil that is exactlly what I will be doing.The heads have received some work in the pockets and a 3 angle valve job. The manifold is next.