Aloha all long time no post.

Yesterday I changed plugs and had one of my Timecerts come out with the plug
I figure I need to replace the head now but then got to thinking with 260,000 + miles on the truck
I might just change out the engine with something hotter. I know some of you have swapped out engines,
My question is where should I start to look for a affordable performance engine?

Mahalo for your advice.