['LIVEWIRE?']

Julie, as others have said, the SAP15/16 devices are Darlington Pairs in one package, whereas the two types you mention are each single transistors, so, whilst not impossible, it would be difficult to replace the SAP devices with BD138/139 or TIP41/42. As a matter of interest I currently have an A3i in for repair. That does use individual transistors - a BD139/2SC 2922pair(NPN) and a BD140/2SA1216 pair (PNP) in a similar circuit, so it's at least theoretically possible to replace the SAPs with the above or similar separate transistors, but a re-design would be necessary, and not to be recommended.