M110 Broken Engine – Options Please?

I previously posted this on the G-Wagen forum...but since this is more engine related then G related, thought maybe could find some good input here....

I am in need of a new engine. The pistons are done. Interesting enough, the engine is real clean inside but my Mechanic theorizes damage is a result of the federalization. Regardless, it does not matter. The options in front of me are;

1. Total Rebuild = $6,800…ouch, but get almost new long-term solution and years of trouble free use. Just don't have this cash laying around.
2. Used Engine = $3,500 (installed)…good compression but still unknown history. Seems like a short-term solution at best. It really kills me that I may have no choice but to go this route.
3. Purchase Rebuilt engine = $4,800 + shipping + Installation…winds up costing the same as a rebuild. Would rather stick with the original engine.
4. New Short Block from Germany = $4,800 + $1,000 (my rebuilt head) + Shipping + installation…could end costing even more then rebuilding.

The truck is in good shape and certainly worth some kind of investment. However, based on reality of the G market, $6,900 is approaching 1/4 of its value or maybe less.

Looking for advise, ideas, or experiences of others. No matter what, I am screwed since the wife is pissed off that my baby is broken and is costing money.

Thanks
MJ
`85 280GE LWB A/T