I have a 69 318 with 29,000 miles on it.

Going to leave the short block alone and use 71 340 heads

68-70 340 exhaust manifolds(already have) or would headers be better headers?

Mopar solid cam??(cant find any numbers on it, how do you read lift on a cam , 273 rockers.

How goo is it to run a solid cam with a blower.

Not totally sure, but I think that 144 will be good to 400hp or so.

Solid cams and blowers are fine. Hopefully you have the smallest of the solid small block purple cams, which is the mp528. Might be a bit much cam but would definitely do the job in a boosted application. Headers would be better but the mp528 has a good rep for working well with hp manifolds.

if you can smooth the ports with a sanding roll and polish the chambers with same and scotchbrite before you get the valvejob.

In my opinion, that'd be a great set-up.
I'd use headers.
We have that same basic set-up in our 1972 Dart using a 53,xxx mile stock 360. The supercharger we are using is a B&M 162 unit.
This set-up runs great as is, but over the course of this winter we're switching to a pair of 2.02" valve heads, supercharger specific carburetor, and some aftermarket valve springs. Debating maybe installing our B&M 174 supercharger, but not sure if that will happen or not.
I can't wait for spring.