Firewall datum from leading edge?

[Gary Wallace]

Anyone know the firewall datum 4 place A??..middlishnas I believei its not perpendicular?

[Battson]

Not 100% sure what your question is, but yes the firewall is not 'normal' to the thrust line.
To measure a distance to the firewall accurately for weight and balance purposes, you would need to know the vertical location on the firewall of the item you're weighing.