[1969400HO]

7K seems a bit out of line for a generic stock refresh on a 400, maybe $4.5K .
I seen stock rebuilds in my area as of last year less then 4K easily but I am not knowing what all s put into them either.
Your complete engine stock or near that, refresh, isn't more than $4.5K IMO, about anywhere.
Where it adds up when you say bigger cam-cut heads to receive big lift springs, balance rotating assembly, (a Must do) new exhaust seats if you think those are really needed, .
A good rebuild w torque plate, line hones, deck block & heads what's really needed etc, etc, I don't see it above that.
I Highly advise you rebuild the damper too, 50+ years old rubber in it like all rubber in these cars are suspect and usually crumbling or deteriorating.
Cliff Ruggles after I spoke w him on this, suggests stock type timing chains, yet I'm mixed on a decision so I would use the high dollar one Butler sells where you change the vlv/crank to 2 or 4 degree advance moving torque a bit lower.

YOU need to bring your engine in directly to a machine shop!!

And controlled 100% of what goes on and what pieces go in it, or if specialty shop pis and delivers it YOU still need to control its full schedule and activity!!

Get engine rebuild Price BEFORE you commit to this specialty shop or the machine shop.

They the specialty shop, have a right to add$$$ to this as this is there livelihood so if they install or pull it that adds into the cost.
Else they would be in business,

Part of this if they are restoring the car the engine build part may be OK with them you control this but R&R it will cost too and they won't warranty the engine whatsoever either.

Its odd in the mind of a specialty shop, to have a shop pull it, you pick / drop off when done and they install it so remember that aspect.

7K is reasonable If they are putting a stroker kit in it and doing head mods to accommodate the extra things like bigger spring perches or pushrod hole elongate etc, as a kit is at least $2.5K yet has other parts in it like slugs/rings, wrist pins etc.
BTW have your Rods-wrist pins made into floaters so rods will need bushings. Thats cheap labor.
So once done a fresh 400engine with a few minor parts will satisfy wonderfully.
And of course the break-in Oil iS essential and filter-oil change in the recommended increments too!
Definitely get roller tips rockers and the good ones, SS stamped, from butler with roller pivot I had on my 69 400 were just fine!