RRC V8 to 300TDI Conversion - Brake Issue?

[iDrive]

Hi

I have a 1976 RRC which has been converted from V8 to 300TDI.

I have two issues;

The brake pedal remains down after it has been used and slowly comes back up - the car continues to brake for a short period after I have taken my foot off the pedal.
Is this likely to be due to the Master Cylinder being different or other work needed?

The heater is pretty much non-existent - Were they any good on RRCs, and if so, how is the diesel conversion likely to have impacted on its efficacy?

Thank you!