Exactly, pcbpage. Racemisation of the D enantiomer is impossible in the stomach as it depends on a number of conditions being met. Whilst the pKa of HCl is one factor, the greatest hurdle against racemisation is fluctuations in body temperature. Furthermore, conversion at 37 degrees C or thereabouts is problematical in itself as the temperature is far too low for effective racemisation to occur. Remember that living creatures selectively utilise only the L enantiomers of the amino acids in enzymes, effectively forming a state of disequilibrium. D-Asp is virtually useless in the body and in general , is only to found in mammalian metabolically inert tissues.
Paradoxically, as the L enantiomers are racemised to the D form after death, their presence can be useful to forensic scientists, marine biologists and paleobiologists etc for amino acid dating.
Incidentally, the exact pKa of HCl is unknown as it’s calculated using thermodynamic data rather than measurement. It’s said to be anything between -4 and -9 depending on the source. This is also of some relevance as far as racemisation is concerned.