[Mr70]

I can't speak for this particular Nova,but Tonawanda records show 18 CKT M/T blocks casted & 10 CKP A/T blocks casted,all designated for 1970 Chevelle A-body useage only.
Only 18 1970 L-89 Chevelles were assembled,so 10 of those blocks were saved for service replacements.
Orders for all these blocks were placed very early on by Chevrolet and soon cancelled within the first few months of 1970 production due to the cancellation of the L-78 equipped Chevelle.
Of the few remaining 1970 L-89 Chevelles I've found,all wore 842 heads as they were 11-1 friendly.
074 heads were 12-1 specific for the 1969 ZL-1 Camaro/Corvette & 1969 L-88 Corvette/1971 LS-6 Corvette.
If this Nova is holding 074's,I'd be curious as to what casting dates are on them as well as what pistons are sliding inside of it.