What capacity will this give all up? Sorry if I missed it.
Is it possible to use the a14 version of this 77mm one and machine it down to get higher compression or will it be too much to remove?

With a bore & stroke of 77 x 77mm my abacus says it comes out at 1434cc. Thats about 23% more than the 1171cc of the original 1200 engine, & it's built with all stock parts.
EDIT. Piston will need machining a small amount.

The A15 stroke is 5mm longer than the A14, so the piston crown is, i presume, 2.5mm lower on the A15 piston. That means that you would need to machine 2.5mm from the A14 crown to make it work.

Just make sure that there is enough meat above the top ring to prevent the crown from being forced down onto it. With a boost in compression you may have trouble finding a suitable fuel for it, & as a consequence, you may need to bring the spark back a fair bit, which sort of defeats the purpose of the exercise.

The larger bowl of the A15 piston gives me a good compression ratio, plus lots of valve clearance, now thats a bonus.

Sounds great a completely square bore and stroke ratio now I put a link up a few months ago bout the new hemi and another about compression from the same internet publication but now cant find it
But it explained that the 92 octane unleaded can handle up to 10.8 compression with the right ignition setup and the 98 octane fuel up to 11.3 compression with the same deal.
Ill try and find it but I would have thought that 2.5mm still leaves a chamber for the valves to miss right?
Either way this engine setup is a dream Dodge and we envy you specially since it will be in your 1k and not ours
That is unless you are taking orders

Flat top, or near flat top pistons may get a little squeezy if you have bigger valves & an exciting cam, so it would be a very good idea to check this with a dummy assembly run.
I dont have an A14 piston here to check, but the top ring may end up a bit close to the top of the piston after is is machined.

I have some stock A14 pistons over at the other house, so if i can find them, i will check it all out with my trusty caliper.
I do not know how deep the bowl is, but i do not recomend machining lower than the surface of the bottom part, all else being OK.

No orders yet, but with the right parts, the whole thing is a standard rebuild, with the sole exception of the machining of the crank, & any fool with a big enough lathe can do it, so you don't need a specialist machine shop.
Mine was machined in a lathe that was made [not just assembled] by my friends father. He even cast all the major parts himself. It is at least 60 years old & is still flat belt driven. Works a treat.

I will see if i can do a photo essay for anyone that wants it when it's done.

Octane.
The compression ratio that a given fuel can handle is to some degree dependant on the design of the combustion chamber & the amount of spark advance.
A high swirl chamber with a very good port design & squish characteristics will handle more advance & compression on a given fuel than a design with poor port design & poor swirl due to minimal squish area.
My Moto Morini 3-1/2 sport motorcycles ran about 10 to 1 comperssion in an air cooled V twin engine. They have a Heron head design & really good porting for extremely good swirl. Thats a lot of compression for the rear cylinder of an air cooled V twin, but it worked a treat.

Itll be a great setup if we can get this kind of crank clearance the way youre going about it. I too aint happy with the a14 markings on my engine and more so the non factory looking engine mount so I will have to consider this option soon before I get pulled over and checked for it.
I agree with not going past the dish section when machining but also would be interested to see if 2.5mm off the a14 piston keeps part of the dish etc.

Heres the article on Compression and getting what you can out of different pump gas fuels. It a good read up.....

http://www.popularhotrodding.com/tech/0311_phr_power_squeeze/

cheers for the link D, very worthwhile reading. I think you might be scratching a bit to try taking 60 thou (give or take) off A14 pistons.

The dish with the offset would potentially offer superior quench characteristics with the small chamber GX head.

Thats a really good piece of journalism, & the 15 points at the end make good sense,... in a race engine, but about half of that would be counter productive in a street engine that is expected to be flexible, smooth, & live long.
On the upside is the fact that the other half is really good stuff for any engine.

I have always said that one of the important elements of detonation controll is good squish. Thank you Mr Ricardo, & thank you D

I don't know, but the combustion chamber of the 1200GX head will see a stroke increase of 7mm & a bore increase of 4mm, so the bowl needs to be a reasonable size to hold compression down to pump fuel friendly levels.

I'm guessing that compression wil be somewhere between the stock 9 to 1 anywhere up to 10 to 1 which is the range that i will be happy with.

is there any difference in the RODs?... is one stronger/lighter?

Yeh have a look at the piston end of the rod, see the hole, its bigger so Dman can run the bigger piston with out rod modifactions.. i think he said he wanted to use the 77 mm piston

with 31cc chambers, 6cc piston dish and 0 deck with 6cc gasket Clearance volume =43cc
Comp ratio = (43 +358.75)/ 43 =9.34:1 I tip.