My suggestion would be to go with a '96 12-valve with the manual transmission P-7100. These were the hottest of the bunch as for stock power levels and a good base injection pump to upgrade on. (delivery valves, plungers, etc).
As far as I know... the 53 block problem didnt affect 12 valves.... it was a 24 valve issue. I have yet to see a 53 block cracked on a 12 valve.... whereas I have seen them on 24 valves. The 12 valve and 24 valve blocks are slightly different (small details) too even though they were both 53 casting. The 53 casting runs were the smaller of the run between the two casting plants anyway.
KDP is a must as TCPDrafting pointed out. Once its done, no worries for life. Cavitation isnt an issue on these engines. I would replace the stock exhaust manifold with the ATS 3-piece unit. Stockers are known to shrink and crack the end ears off sometimes. Also check the starter contacts for wear and burning. Replace with one of those starter solenoid rebuild kits. (Cant think of who has the popular one... name escapes me at the moment).
Everything else of my suggestions are all power tips.... (Piers ported-ringed head, twin turbos, swap intercooler with a 24 valve one, etc.)
