5.9 Mag stock LB or rebuilt SB

JTinAZ said
I need you alls opinions. I’m looking for a 5.9 magnum for my 69 Dart build. I’ve found a complete stock LB with supposedly 96k miles on it. I’ve also found a rebuilt .020 over short block with new stock cast pistons, new lifters, cam (not one that I would use), oil pump, etc. fully assembled and never installed. Prices are close enough that it’s not a decision factor and I’m going to replace the heads regardless so the long block vs short block isn’t a big deal either.
My question is which would you prefer to start with? I’d like to get to 400 hp and this will be a street only car, no racing. Do I need to replace the stock pistons to get the CR higher to get to that HP or can I get there with stock pistons, aftermarket heads, intake, cam etc? I’m leaning towards the short block, but I don’t know the quality of the build. If I go with the long block I was hoping to get by with just new bearings and a hone.
I appreciate any feedback you all have.

I picked up a 96k long block locally for my Dart.
Still obvious cross hatching in the bores, and the crank and rod bearings looked near new.
The heads were garbage with cracks and horrific valve seats, which I expected.
I put a set of LA drilled New Zealand EQ heads on with Hughes springs, retainers and locks from a V6 that allows up to about .525 lift.
Oregon Cam Grinders.512 lift and 214/224 duration and 110 LSA (torque with a little sound to it)

You might find the same used condition on the long block, but assume you will need heads, cam and timing set at the least.
On the rebuilt short block I wouldn’t be comfortable without being able to verify.
Too much BS in the world.