Jeez, I guess I'll weigh in and offer one of my past experiences:
Before one of my mates accidently stepped in front of a b-double on old Toongabbie road last year, he built up a 308 for his 85 hilux.
Red motor 308 Turbo pattern block out of a HJ Statesman (QT prefix)
Bored 60 thou
0 Deck height
Flat top pistons
Fully balanced and blueprinted
L34 Heads and L34 Cam
Straight Gas (easier to get the conversion approved by Humpries.... well humpries isn't in business anymore but I'll tell the story of him going to the US and coming back as the opposite gender in another tale......)
It pulled hard from the get go but was lacking up the top end but the hilux he intended to be a "recovery" vehicle and for his own fun.
At the end he tried a VN top end with a 185 HSV cam and it revved so much more freely but it's torque only came in at a short gob compared to the pre efi heads.
In your position I'd go a similar direction with early heads as they have a wider torque spread/band compared to vn heads.
Holden never really made heads for the 308 specifically until the VN, pre efi heads were identical (stock) for 253 and 308.
The key is increased capacity and compression, small/mild cam and early heads.
Balance, blueprint and port match everything but be careful with any porting of your heads, you want the flow to have velocity.