Trying to figure out if its worth going with long tubes over shortys on a stock long block 350 TPI with bolt on modifications and free mods. Basically everything that can be done besides changing the camshaft or touching the heads. Also keeping the TPI, no stealth ram, mini ram, etc. Also looking for opinions on primary size. I see the ebay long tubes but they are 1 3/4. Hedman offers a pair of LTs with 1 5/8 primaries which I feel is better suited for this setup.

 

Hard to say if it's worth it. That's for you to decide. Headers are great, but also come with a lot of hassle. If you are up for dealing with the cost, fitment/clearance issues, moving wiring/lines/etc. so they don't burn, then go for it. Long tubes are going to be more of a challenge than shorties with a y-pipe.
On a relatively stock motor, headers will make a difference over stock manifolds, but won't be much difference between shorties and long tubes. Use a good high flow catback exhaust system (any of the 3" catback systems are fine, just your preference on sound). As for 1-5/8" vs. 1-3/4" primaries, on a relatively stock motor, not a lot of difference, but if you are planning for internal motor upgrades in the future, then 1-3/4" would be better.

I went with Dyno Don shorties on my built, just because I didn't want to deal with the long tubes. I left a few HP on the table, but that's OK.

 

W a tpi you'll be fine w a good set of shorties. A set of full lengths isn't worth the hassle. You're not making enough power up high to need the full length headers. Get a set of dons headers, you'll be cool. I have a blower on a sbc that put 470 to the wheels and I'm using dons headers. I did have the y pipe cut so it merges the 2.5 in pipes into a 3.5 vs the 3 inch they come with. Maybe I could make more w a set of full lengths but I don't think it's worth the time/fab to make it happen for a couple of hp. Plus these cars have enough ground clearance issues, why complicate it more.