Vangm25 mentions clearances... is your engine knocking, bottom-end knocking, as in bad rod bearings?
In the bad old days, when I rebuilt 3 engines (1972 Dodge 225 slant 6, 1979 Honda Civic, and 1970 British Cosworth-modded Ford 4), rod bearing clearances were pretty sloppy. They were easy to check with Plastigage. The flow in the oil galleries was easy to check with a pump type oil can.
Have you checked out professionally re-built engines for your car? This thread: https://www.toyotanation.com/forum/1...ort-block.html
has a good, succinct discussion of sources and some info on costs.
Or used engines? I sort of exaggerated when I said I rebuilt
my slant 6 - I replaced
it with a very low mileage used engine, but I tore that used engine down and checked everything, including all bearings, then re-ringed it, complete with re-honing of the cylinder walls. Thing is, the '72 had a whole lot less stuff hung on it - no sensors to speak of, no ECU or related electronic stuff, push rods instead of OHC, and basically just a distributor, oil pump, and alternator.
It's not impossible to rebuild, in fact some elements are fun, but you sound as though this is your first venture into this sort of thing.
What manual are you using? I had the Dodge factory manual and a very good aftermarket Honda manual, plus access to real manuals for the latter at our public library. I didn't have anything for the Cosworth.
The Dodge went another 75k and 6 years before we sold it. The Honda went maybe another 50k before rust killed the car. The Cosworth - remember, no manual - went about 75 miles in 2 SCCA races before two rods let go. Couldn't get new rod bolts for that, they were no longer made, and just stayed with the originals and prayed. Clearly, the prayers were not answered.
The slant 6 and Cosworth had to come out. An engine stand is a blessing in this case and Harbor Freight is your friend ($60 or so). The Honda stayed in the car but made for a lot less fun.