Take the 5.3 swap every time and don't look back. A 140k mile truck engine has way more life left than a 4.3 you're patching with bearings and rings, that old engine is still a 4.3 at the end of the day. Cracked injector pin is just a $20 connector and an hour of soldering, that's nothing compared to pulling a transmission and resealing an oil pan twice on a rebuild. Your buddy's S10 will be smooth until it ain't, and when a rebuilt 4.3 lets go it usually takes the cam with it. You got one bad wire, he got a ticking time bomb with the same money spent.