i remember looking that stuff up recently for my small block. a maltese cross meant oversized lifters or something. just web search casting numbers and engine i.d. codes/bosses and you should come up with meanings. hc was used to identify high compression, hp = high performance. i've never encountered "ht."
for 65 engines:
http://www.1962to1965mopar.ornocar.o...ification.html
hope that helps