Obligatory "total noob here". So I have a 300sd that I would love to keep the original om617a in due to the car having a lot of sentimental value to me. My goal is 300 horsepower but it seems that 250 is a more realistic goal with the om617a... My current lineup for mods is:

7.5mm elements pump
Much larger turbo
Straight pipe exhaust (can't decide between 2.5" or 3"... Any input?)
Custom exhaust manifold
Swap the auto trans for a custom manual setup.

I have no clue if this will get me near my goal.

At this point though I'm unsure if I should even try this and just bail out and pay someone to help me with an om606 swap. Once again I would really hate to swap out the om617 because its such a quirky engine and having the original one in would mean a lot to me. Its cool having this inline 5.

What would be the most realistic and cost effective approach? I will definitely have to pay my mechanic here and there for help especially on the transmission swap and fabrication on the manifold if I stick with the om617. So labor costs are definitely a factor.

Thanks in advance and sorry if this comes off as silly or stupid.