New Build Advice Needed

All of that is great information and thanks so much!

250-300 hp is a “number” that I was thinking because we currently have a little Toyota car that makes about 250hp with a 3.5L front wheel drive and it’s a blast to drive.
I once owned a BMW M3 that was a little roller skate and I think it was about 300 with it’s in line 6.
I just thought that level of power with a broad torque range of a slant 6 in something you don’t see every day would be super cool and different. (And yep, it sure costs more to be different)

my general thoughts are fuel injected and turbo slant. What guts does the short block need to hold up? Cam selection? Vendors?
Head? Spring pressure? Porting I get but does it need oversized valves or is a good angle job enough with a balanced engine?

the intercooler I get is key.

I’m not knowledgeable yet about the “long rod” using the 198 rod?

I’m pretty sure I’m going to have to have a torque convertor custom made.

I intend to keep the old push button trans but I know from my old stock eliminator days that a properly built 904 with handle 300hp because everyone was using those guts behind big block cars in the 80s.

Keep the information coming please. Learning a ton!