> no ADS
> you have sufficient time from the confirmation day to the actual race day (min 6-8 weeks)
> your VO2MAX is lower than 75
I would do a highly polarized training w/ 90-95% of Z1 and 5-10% Z4 (VO2MAX-Training). Start w/ 5% Z4 and see how you tolerate that. 6 to 8 weeks prior the race I would switch to the very specific event training: when your event is Z3-based train Z3 (still highly polarized), when your event is below AeT go with Z1/2 training + ME (w/ some Z3).
Let me know if you have any questions.