The connecting rod is a key component in the air cooled VW engine. Let's look take an in depth look at it and see how it compares/contrasts with the Type 1.
This connecting rod is from a 1.7L Type 4 engine. The 1.8L are almost identical to this, but have a slightly larger block on top of the small end (wrist pin end). One word has been used to describe the 1.7/1.8 rod: beefy. It's quite a large and hefty component, but it shares a common weakness with all of VW's connecting rods in the Type 1 and Type 4: weak rod bolts. The rod bolts are known to break under severe use.
Above us is a 2.0 L connecting rod. It is similar to the 1.7/1.8L rod, but does have the balancing pad (block) on the small end. It also features a smaller diameter "big end". The 1.7/1.8s use 55mm diameter rod journals, whereas the 2.0s used 50mm. The extra 5mm went to increase the stroke of the crankshaft (66mm to 71mm). These rods are quite expensive, even as cores. The desirability of increased displacement, coupled with the relative scarcity of the 2.0 engine (especially the VW/Porsche 914) has made the price exorbitant at times. A resourceful junkyard scavenger should be able to find a Transporter 2.0 for a reasonable price. The rods are identical regardless whether it was in a Bus or a 914.
Compare the Type 4 rods with the Type 1 1600cc rod above. The Type 1 rod looks rather fragile in comparision. The Type 1 1600cc rod features a 53mm diameter big end, 22mm diameter small end and the same inherent weakness with the rod bolts.
Here we see all of three of the rods laid out side by side. Obvious from this photo is the longer center-to-center length of the Type 1 rod. The shorter rods of the Type 4 moves the RPM band farther down and makes the engine better suited for the heavy 411/412 and the boxy Transporter. These two vehicles need more bottom end grunt to get going and to keep accelerating up hills.