ALL HP blocks were fitted with steel cranks. Which are stronger and rev harder and higher than the standard crank.
The HR X2 model did NOT come with a two barrel WW Stromberg carb. X2 was the official model denomination for Twin single barrel down draught Stromberg carbs.
The EH had a model released known as the S4, this was Holden's first factory "Performance" car, it had wider brake drums and shoes, a very mild cam and only came with a high comp 179. There was no option for Automatic in this model. It was quicker than the standard EH but not by much.
There were four engine options in the EH, both low and high comp versions of both 149 and 179 engines. The HD carried these engines over, adding the twin carb, 2 piece header in the X2 version.
The compression rating was all in the head, it's got nothing to do with the block. On the passeger side of the head there is either an L or an H cast into it about 2/3's of the way down towards the rear end of the head. L for low comp and H for high comp.
When the HR was released both 149 and 179 were replaced by the 161 and 186, again both high and low comp version plus the X2 twin carb with 2 piece headers as featured on the HD.
The JP block as used in LC and LJ GTR and GTR-XU1 was also fitted with the steel crank. They are highly sought after items among the Torana crowd.
The engine number will help identify the cubic capacity of the block in question. Google some car clubs and they'll be happy to help you out.
An HP block with either a steel crank or a black motor internally balanced crank with the "starfire" rods as fitted to the starfire four cylinder in VC commies and Toyota Corona's and also black motors with a high comp head, 40/80 solid cam and multiple carbs with the black motor's electronic dizzy make for one hot sixpot. Factory bits put together in this combination are tough and reliable with good horsepower outputs. In an early Holden EJ, EH, HD, HR or a LC LJ Torrie, this combo will give most 5litre VN-VS a run for its money. My Uncle has an LJ 2 door with triple Dellortos and a Celica 5 speed with a very similar combo to what I've described above and has run 13 second passes at Eastern Creek.