I voted for both the intake and heads.
When I bolted up my GT40 intake, 65 TB, 24#ers, and 75mm Bullet, I was expecting a huge gain and just didn't see it - this was with the stock E7TE's.
As soon as I installed the TFS TW heads and Steeda cam the car came alive.
As Dark 5.0 has said and done, it is possible to see gains with ported stock heads, and new intake, etc. but it will be 'harder' to do.
If it were me, I would save up the cash to do everything (read: intake, heads, maybe a cam too) at once.
Good luck with your decision.
E
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1991 5.0 LX Coupe - 40,750 miles
331 cu. in. / Tremec 3550 / BFG Drag Radials
12.22 @ 114.31 mph - w/1.89 60'
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