Yes 906 heads are fine, but not with a piston that is speced to be used with a 516 sized/shape combustion chamber.

Tons of race engines USED them because they were all they had to use, or the class specified them, otherwise they are a POOR choice, especially in a 383 that is hard to build compression in to begin with.

I just did the math, 90cc head, .041 gasket that is in the kit he bought, a piston .087 in the hole on a blueprint block (1.848 ch), his block may be a little taller, 7.52 compression ...

He's got a 383 not a multi dollar blown Hemi. What he's got will make a good street engine for the money he's ALREADY spent. What ever we spend for the good heads here in the states, double that for him over there.

I'm not saying he needs to spend millons on a head, it is what it is.

Are you ASSuMEing he has a super duper PORTED head off someones race engine? In stock form a 383, in a car weighing almost 4000 lbs, overcammed is going to be less than impressive, especially with 7.5 compression...

Hopefully joining that group SuperRob mentions will garner him some help , hopefully parts wise and finding a capable shop that can build that engine right.

I have a 383 Engine oversize 0030
Original Crankshaft Original Rods
with the Rebuild Set from Summit
Federal Mogul Premium Engine Rebuild Kits MKP-667E300
And a 8 3/4 Axle
I don´t have a transmission or camshaft , air intake
i want to use the original heads 906 because i like the original .
i dont want a race engine
i want a little more than the original engine was.

For a street 383 in a fairly heavy car, been there & done that, and here's what I'm thinking given what Felix has told us so far:
You can either return the piston kit and get one with more compression from the same source, or look at 440source.com and see what they have. A cast piston will be fine but forged holds up better to detonation.
Not knowing the octane ratings in the Fatherland, I wouldn't want to go more than 9.0:1 on an iron-head Wedge @ 91-92 octane.
The Edelbrock cam is kinda short on lift, but IF you also need rocker arms, a 1.6 ratio would help that. Otherwise, look at more modern stuff like the various Comp Cams, Engle choices. Something in the 214-224 @ .050 and around .450-.480 lift will be mild enough for a stock converter at 9.0:1 CR. I've used as much as .504 lift at that duration with tall gears & stock converter and had very nice street manners.
With old stock heads & block, a surface cut is likely needed for flat decks on both. Good machine work, balancing, and a good valve job go a long way; find a GOOD machine shop that's familiar with American engines and has an eye for details. There's maybe .5 CR there without going nuts.
I like double springs on the valvetrain, and at least a windage tray. Use a dual-plane intake (look in the ads here for nice used), and a 650CFM carb would be adequate.
The Eddy & Stealth heads I've used all needed a better valve job, and the springs & parts were OK.

Gas stations max out at 95 octane (called ultimate102 over here).

If he could find even a set of 516 heads over there those with a little porting and 1.74 valves that would be better than the 906's , but he would need to get a piston that is closer to zero.

DO NOT HACK .087 off the deck to get those pistons at zero , it would be cheaper to just buy another set of pistons from summit and have them shipped over. Which wouldn't be a bad idea,in the long run that will save him money.

I would go with a dual plane intake & a fairly small carb possibly one of the newer ones that all the metering systems are adjustable. Holler what parts you go with & how it turns out (if it meets your expectations)

I just went through this on my 67 383. I bought KB pistons and on paper I was to be at 9.0:1 compression. Measured came in at 8.2:1 and I cried.

I fortunately was able to recover by milling the 915 heads 0.040 inches and that got me to around 8.9:1 (from what I recall - could be a tad less). But that was with a closed chamber head - the open 906 head puts you in a much worse position.

What does it really matter if it's 8 to 1 or 10 to 1 on a STREET engine. It's a done deal for him, get the cam and induction right and he'll be fine. I dought he has the three figure income like you guys on here that can just buy all those high dollar parts, he's making do with what he has. Help him out and quit telling him he has junk (which he doesn't).

a 3-figure income would be max $999 a year...

As opposed to the regular compression-wasting thick 0.039" FelPro headgaskets, one can use steel 0.020" headgaskets to increase the CR a bit.

Also, before you go ordering a 'new' transmission, there used to be a time when 'TCI' was better known for Total Crap Inside...

IMO, a normal/stock 727 will be beafy enough for your use.

a 3-figure income would be max $999 a year...

What was I thinking? I guess what I make. LOL

If you haven't rebuilt your heads yet, you might consider the Edelbrock E-Street heads. The 75cc e-streets, part # 5090, are around $1300, available trough Summit, and would bring compression up to 8.5:1.