LA360 compression

ok engine builders. Here is my dilemma. I bought a Mabbco rebuilt 360 short block from a member. Some upgraded stuff like KB high compression flat top pistons, moly rings, 272 muscle cam (272/272 duration 454-454 lift) Cloyes HD timing chain and sprokets. .30 over bore. Got a nice brand new set of Speedmaster aluminum heads with 68cc combustion chambers.
Here's the problem; my engine is at a builders for finishing. Went by there yesterday and he said this engine will be an absolute dog as it sits now. He doubts it will make 8:1 compression. Yes, the pistons are below deck a little, but he says I am losing a lot of quench with them. He suggests new pistons, rods, roller cam and new crank. That's an expensive prospect, considering what I already have in the motor. Also, this guy is a very well known builder with a great reputation and is well known in the racing circuit. His shop is incredible and he rebuilds engines for a living, and has many many great reviews. He does not even want to assemble the rest because he says he knows I will be disappointed.
What to do? Will this motor be a dog like he says? I don't know that I have the scratch to have him tear down this motor and upgrade it to a stroker.
TIA.
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If somebody sold you that short block assembly saying it had KB107 pistons, they lied.

The good news is the engine builder you have now is NOT screwing you. He is correct about the pistons being low compression. But, if he does not want to deal with this unless you get another rotating assembly just use another builder. There is a likelihood he is expecting a **** show if he opens up the bottom end, to help move it along he says start over. That is reasonable.

If you want this short block with more compression, you just need actual KB107 pistons, possibly a new balance job since the KB107 may be much lighter, and then you are good to go.