(b) Exceptions.--(1) If before the expiration of the period of limitations for assessment of liability of the transferee, a claim has been filed by the administrator in any court against the original taxpayer or the last preceding transferee based upon the liability of the original taxpayer, then the period of limitation for assessment of liability of the transferee shall in no event expire prior to one year after such claim has been finally allowed, disallowed or otherwise disposed of.

(2) If, before the expiration of the time prescribed in subdivision (a) or the immediately preceding paragraph of this subdivision for the assessment of the liability, the administrator and the transferee have both consented in writing to its assessment after such time, the liability may be assessed at any time prior to the expiration of the period agreed upon. The period so agreed upon may be extended by subsequent agreements in writing made before the expiration of the period previously agreed upon. For the purpose of determining the period of limitation on credit or refund to the transferee of overpayments of tax made by such transferee or overpayments of tax made by the transferor as to which transferee is legally entitled to credit or refund, such agreement and any extension thereof shall be deemed an agreement and extension thereof referred to in subdivision (b) of section sixty-seven. If the agreement is executed after the expiration of the period of limitation for assessment against the original taxpayer, then in applying the limitations under subdivision (b) of section sixty-seven on the amount of the credit or refund, the periods specified in subdivision (a) of section sixty-seven shall be increased by the period from the date of such expiration to the date of the agreement.

(c) Deceased transferor.-- If any person is deceased, the period of limitation for assessment against him shall be the period that would be in effect if he had lived.

(d) Evidence.--Notwithstanding the provisions of section seventy-eight, the administrator shall use his powers to make available to the transferee evidence necessary to enable the transferee to determine the liability of the original taxpayer and of any preceding transferees, but without undue hardship to the original taxpayer or preceding transferee. See subdivision (e) of section sixty-nine for rule as to burden of proof.