Cracked 350 Crank, build 383?

[teeteeplz]

Hey hoping to get some suggestions as to an economical yet fun solution to my recent dilemma.
Ive got a 1972 C-10 with a jasper reman 350SBC (quadrajet, stock manifolds, stock build i believe) installed in 2014 and ive put about 20k miles on it since the install.

Last week or so I noticed a knocking of a two tones (hi,lo) near the motor and noticed the harmonic balancer was hitting the timing tab, and had more wobble to it than normal. I bent the tab up a bit hoping for a quick fix, until i got the time and $ to replace the original harmonic balancer. it took care of the pinging of hitting that timing tab, but a deep knocking remained, faint at idle until hot, and noticeable with the vehicle at 0mph and the truck in gear (auto th350 trans). oil pressures seem normal

I dropped the truck off at my local repair shop for further investigation, and possible harmonic balancer replacement. when they popped it off, they noticed (and I later verified) a large amount of play on the snout? of the crankshaft. They claim that it is cracked, and others have told me that it has broken in a way that is allowing the motor to run but is on very borrowed time. The motor has never been overheated to my knowledge, but was installed by a rather inept mechanic prior to my ownership.

Is it safe to assume the Crankshaft is toast at this point and requires engine removal from the truck, crank replacement, and Main bearings done while in there? How much would this cost for a minimal fix with new parts? Is this a smart solution?
Would I be better off Building a 383 stroker out of this lightly used 350 core,reman 350SB? As the Crank sounds like its in need of a replacement anyhow. Or should I buy a crate of some sort and dump this 350?

I believe the rear end gear ratio on this truck is a 3.08(3.07?) as my tach is just about 3k if im doing 85mph with 265/75/15. I dont have known any issues with the TH350.

-true dual exhaust flowmaster 40's

The truck has been in my family since around 94 and has a lot of sentimental value. I appreciate any recommendations on what I can do to add some fun with out a second mortgage

the only other modification I really want for this "rebuild/repair/replacement etc" Is switching to Posi-trac. One wheel burn-outs just arent cutting it!