Want to make more power in my s123.

Hi everyone, I'm new to the forum and I have some questions that I've been looking for answers to for quite a while but haven't found much of anything that is helpful. Ive searched all over the internet, but this seems to be largely undocumented territory.

I have an 84 s123 with an om617.950 or .951 from a 300sd (assumed since I know the engine was replaced before I bought the car and it has a tach pickup off the crank pulley). I want to make more power, but I am unsure what a reasonable figure is or if anyone here has any experience modding 617s in a 123 (I assume it will mostly be the same as in a different vehicle). I preferably would like to make between 2 and 3 hundred hp at the crank. What I am trying to achieve is as much power as possible while retaining the stock drivetrain and brakes (though they might have to go eventually, even with the stock 617 they feel like they aren't enough) on my 123. Additionally, I know that the transmission is built to handle roughly 300 ft-lb of torque, though I am unsure on the rear end and have seen the diffs explode even with less than 400 ft-lb of torque. So, basically, I want to know:

Is 200-300hp an attainable figure with just a tub or fuel pump or both

Is that much hp safe on an otherwise stock 617 that is daily driven and often driven at about 80mph or something like 3500 ish rpm (not exactly sure this is an estimate my tach does not work), if not how much is?

What combination of components should I use to achieve my goal (like what turbo and what aftermarket pump)

Will I need to improve the cooling system as well if I make more power?

What oil do you guys use when making this kind of power? (currently using 15w-40 and I'm in southern cali)

Oh, and lastly just a few more notes on my car that may be of concern;

My engine has about 160k miles with no rebuild, valve adjustment in the last few thousand miles and blowby is minimal. I have idle oil pressure around 25-35, and 45+ under load (not super sure as the pressure gauge ends at 45 and it maxes out under load). The timing chain and tension is in great shape. The coolant is a bit rusty from years of neglect, but pretty minor and has improved under my care. Additionally, coolant temp at warmed up idle is about 80 celsius, 85 under normal load, and hit 90-100 when under high load and high RPMs ( for a long period of time, doesn't ever go higher)