Stay with bits from junked Falcon GL 5-speed 3.3 or 3.2's, or ex taxi AU rods. Gotta be some cheepies there. Then grab a book from a reputable engine builder, like Smokey Yunick, Grumpy Jenkins, or David Vizard, and read about rod preporation. Do it yourself. Get them magnafluxed and checked with die penatrate. If they cut muster, it'll be darn hard to break either of them. Rod bolts are the key. Most guys look to good ARP Windsor bolts, or bigger SPS big block Chev bolts depending on the original size.
The Astron 80 2.0 and 2.6 engines have robust 6.5" rods (1976-1984, and 1979-1996). They have a smaller rod journal (Cortina/Pinto size), smaller wrist pins (Holden red-blue-black/BMW/Nissan L-series). They are designed for 6000 rpm+ in the 2.0, and over 5000 rpm in the 2.6. Later ones in Magnas got to see 6000 rpm. All with a Falcon -like stroke of 98 mm.
The Mitsi rods would be okay as long as you can scrape together a bushed piston and turn down the cranks big ends. Lots of 'ifs'
To ruin a Clint Eastwood saying:-"Do you feel
rich? Well do ya, punk?"
The smaller Diesel con-rods from Golfs and Passats are excellent for Holden red-blue-black engines, but at 5.35", they are too short for a 250. They run puny Holden crankpin sizes too. They are way too short. So are the LD28 Nissan diesel pistons. As the engines get bigger, the wrist pin gets huge, and the bigger diesel V6's, V8's and I4's won't fit in the confines of a Falcon piston.
Other options like 350 Olds diesel pistons and such-like are the right size for a stock 250, at about 5.886", but whats the point?
http://www.442.com/tech/enginearticle.html
CID___ YEARS___BORE___STR.__ Jrnl._Mains__Conn.__Piston
______________________________Rods__Dia.__Rod___Comp. Ht
350D__ 1978-85__ 4.057__3.385__2.12__3.0___5.886___1.770
Until I see inventory on other post 1985 engines, I can't say what else will work. Bound to be something!